A Research Guide for Students by I Lee

Measuring Time

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Daylight Saving Time
History and Science of Time
Leap Year
Lesson Plans on Time
Local Time and Time Zones
Measuring Time - Clocks
Measuring Time - Sundials
Miscellaneous Sites on Time


The 10,000-Year Calendar! With this calendar you can view a month or year calendar for any year from 1 to 10000 A.D. Site provides an explanation on how to use the perpetual calendar, plus Free Calendars, Calendar Converter, Calendar Links, 100-Year Perpetual Calendar, and Download Center where you can download a printable copy of any kind of calendar, including the 10,000-Year Calendar in the format of your choice.

2022 Yearly Calendar | One page Calendar. A one page calendar. All 12 months of 2022 on a single page. Download 2022 Printable Calendars.
2023 / 2024 Two Year Calendars for PDF from Calendarpedia.com. Free printable two year calendar templates for 2023 and 2024 in PDF format. Also available: Yearly calendars, Quarterly calendars, Monthly calendars, Weekly calendars, Daily calendars, Hourly calendars, Split year calendars, School calendars, Academic calendars, Fiscal calendars, 2 year calendars, 3 year calendars, Photo calendars, Birthday calendars, Blank calendars, Perpetual calendars. Online calendars.
2023 Calendar from Calendar Labs. 2023 Templates. 2023 Calendar. Calendar Categories include: Astrology Calendar, Desktop Wallpaper, Blank Calendar, Daily Planner, iCal Calendar, Custom Calendar, Online Calendar, Long Weekends, PDF Calendar, Word Calendar, Excel Calendar, Printable Calendar, Photo Calendar, School Calendar, Family Calendar, Accounting Calendar, Fiscal Calendar, Business Calendar, Julian Calendar, Bank Holidays, Market Holidays, Netflix Calendar, 2023 and 2024 Monthly & Yearly PDF Calendar Templates, Quote of the Day. Example: 2023 Year at a Glance Calendar Canada Holidays. You can customize your template.
Free PDF Calendar from Calendar Labs.
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Word Calendar Templates, PDF Calendar from WinCalendar.
Free Printable Calendars from print-a-calendar.com.
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Calendars from The Time Now. This site has been evaluated as more accessible for the vision impaired than most other sites. Also, you can print out calendars from AD Year 2023 or earlier to Year 999999999999 in case the earth lasts that long and calendars are still used.
Make Custom Calendars Online from Custom Calendar Maker. With this online web app you can make your own custom calendars for 2023, personalize it with your photos and download it as a PDF file for easy printing. It's free!
Printable Calendar Templates. Create printable calendars formatted for Microsoft Word®.
Free Printable Calendar Templates, Planners and More from BlankCalendarPages.com, a United States based website that brings you simple, elegant calendar pages. You can download templates for free and print: blank calendar, Monday calendar, monthly calendar, yearly calendar, holiday calendar, portrait calendar, etc. with 55+ styles to choose from in various languages.

Ancient Calendars - Aztec, Egyptian, and Sumerian Calendars - Stonehenge from Inventors.About.com. See also Other Ancient Calendars from Calendars through the Ages.

Ancient Egyptian Calendar. "The exact origin of the ancient Egyptian calendar is unknown, but it is estimated to have started around 5,000 years ago." The Ancient Egyptian Calendar from Journey to Egypt.com. The Egyptian calendar was broken down as follows:
One week was ten days.
Three weeks was one month.
Four months was one season.
Three seasons and five holy days was one year.

Aztec Calendar Wheels, Central America, 1000 BCE by Kate McCloskey, Smith College Museum of Ancient Inventions.

Babylonian Calendar from Calendars through the Ages.

Baha'i Calendar from Calendars through the Ages.

Balinese Calendars. Balinese use two calendar systems, the Hindu Çaka and their own Pawukon, from Calendars through the Ages.

Calendar from time and date.com. Create yearly calendar: Choose a Year and Country - includes Holidays and Observances for selected country. Or Create calendar by month.

Calendar from Wikipedia, the free encyclopedia.

Calendar 365. 365 days - a calendar at hand. Year calendars, Handy dates (Daylight Savings - Start times and dates for the next 15 years, Holidays for this year and the next 5 years, Leap years, Seasons - Meteorological Seasons Astrological Seasons for Northern and Southern Hemispheres, Week number), Moon phases (Current moon phases, Moon calendar, Moon phases), World Clock, Calculate (Period between two datess in number of years, months, days, hours, minutes, seconds).

Early Roman Calendar. The Romans borrowed parts of their earliest known calendar from the Greeks. The calendar consisted of 10 months in a year of 304 days.

Ancient Everyday - Telling Time in the Roman World from Eagles and Dragons Publishing. The Romans did indeed have clocks, or horologia. Horologia could come in two forms. They could be solaria (shadow clocks or sundials) or they could be clepsydrae (water clocks).

History of sundials from Wikipedia. The earliest household clocks known ... are the shadow clocks (1500 BCE) in ancient Babylonian astronomy ... The ancient Greeks developed many of the principles and forms of the sundial. Sundials are believed to have been introduced into Greece by Anaximander of Miletus, c. 560 BCE ... The Romans adopted the Greek sundials, and the first record of a sun-dial in Rome is 293 BC according to Pliny ... The Romans built a very large sundial in 10 BC, the Solarium Augusti, which is a classic nodus-based obelisk casting a shadow on a planar pelekinon ... The custom of measuring time by one's shadow has persisted since ancient times. In Aristophanes' play, Assembly of Women, Praxagora asks her husband to return when his shadow reaches 10 feet (3.0 m).

Archaeologists Uncover Rare 2,000-year-old Roman Sundial and it Tells Them More than Just the Time from Ancient Origins. A 2,000-year-old intact and inscribed sundial - one of only a handful known to have survived - has been recovered during the excavation of a roofed theatre in the Roman town of Interamna Lirenas, near Monte Cassino, in Italy.

Measurements of Time in Latin by Brittany Britanniae, Latin Language, Roman culture, Mar 12, 2015. The Romans time of day was divided into 12 hours (Latin: horae) of light and 12 hours of darkness. The Romans also divided the day into other periods, such as media noctis inclinatio "midnight," gallicinium "cock-crow", conticinium (with variants such asconticuum) "hush of the night," and diluculum, "decline of the day" ... The complicated Roman calendar was replaced by the Julian calendar in 45 BC by Julius Caesar ... The Romans used various timekeeping devices including the clepsydra, or water clock, and the Greek sundial.

History of the Calendar.
Astral themes. Days, months and years. Lunar and solar years. Julian and Mayan calendars. The working week. Jewish and Muslim calendars. Gregorian calendar. French republican calendar.

Why Seven Days in a Week? By Peter Meyer.
Our Seven-Day Week from Calendars through the Ages, including: What Is the Origin of the 7-Day Week? What Do the Names of the Days of the Week Mean? What Is the First Day of the Week?

Calendar Zone: Bring Order to Calendrical Chaos! Links to a wide variety of calendars, including shopping and advertising sites: Art, Celestial, Cultural, Daily, Event, Geographic, Historic, Holidays, Interactive, Misc. (includes: All the phases and eclipses of the Moon), Reference, Reform, Religious, Software, Traditional, Web, and Women.

Calendars and Their History by L. E. Doggett. Introduction, Astronomical Bases of Calendars, Calendar Reform and Accuracy, Historical Eras and Chronology, The Gregorian Calendar, The Hebrew Calendar, The Islamic Calendar, The Indian Calendar, The Chinese Calendar, The Julian Calendar.

Calendars through the Ages: Calendars from the Sky. Topics covered: Our 7-day week (origin and meaning of names of days of the week), Our year, Calendars (Christian, Jewish, Islamic, Chinese, Mayan, etc.) plus other unusual and interesting subjects relating to time and calendars.

Calendopaedia - THE Encyclopaedia of Calendars. Contents: Comparison of Calendars, Astronomical Calendar, Julian Calendar, Gregorian Calendar, Other Calendars, About Time, and Links to Other Sites. Includes a Complete Index of the Site.

Chambers's Book of Days from University of Wisconsin-Madison Libraries. A Miscellany of Popular Antiquities in connection with the Calendar an electronic reprint of the original: Chambers's Book of Days. Philadelphia: J. B. Lippincott & Co., 1879.

Chinese Calendar from Travel China Guide. "Chinese calendar, a lunisolar calendar, is formed on the movement of the moon. It defines Chinese 24 solar terms, traditional holidays and helps to choose a lucky day before important activities such as marriage proposal, wedding, praying for pregnancy, traveling."
Western-Chinese Calendar Converter from Mandarin Tools.
Gregorian-Lunar Calendar Conversion Table of 2023 from Hong Kong Observatory.
Chinese Calendar Conversion * Convert Chinese - English Date from Prokerala.
Generate Chinese calendar for any month, any year from Prokerala.
The Mathematics of the Chinese Calendar by Helmer Aslaksen, Department of Mathematics, National University of Singapore. Draft: March 29, 2006. "Chinese New Year is the main holiday of the year for more than one quarter of the world's population. In addition to China, Taiwan, Hong Kong, Macau and Singapore, it is also a public holiday in South Korea, Indonesia, Malaysia, Brunei, Laos, Vietnam and Mauritius. Very few people, however, know how to compute its date ...
Since the fourth century BCE, Chinese astronomers knew that the motion of Moon was irregular, and since in the sixth century they knew that the Sun's motion was also irregular. They had started using the true Moon in the calendars since 619, but until the time of the Jesuits, they continued to use the mean Sun ..."

The Mathematics of the Chinese Calendar from Chinese Outpost. Noted by Dr. Helmer Aslaksen of National University of Singapore: "The main focus on my paper is the study of leap months in the Chinese calendar.
In the early 1990s, Chinese astronomers discovered that there was an error in the Chinese calendar for 2033. The traditional calendar claimed that the leap month would follow the 7th month, while in fact it comes after the 11th month. It is very unusual that the 11th month has a leap month, in fact it hasn't happened since the calendar reform in 1645 (before 1645, all months had the same probability for having a leap month). But many Chinese astronomers still claim that there will never be a leap month after the 12th and 1st month.
I have found that there will be a leap month after the 1st month in 2262 (in fact, it should have happened in 1651, but they got the calculations wrong) and there will be a leap month after the 12th month in 3358 ..."
Chinese Calendar from Your Chinese Astrology.

Chinese Calendar from Time and Date.com. The Chinese calendar is lunisolar. It is based on exact astronomical observations of the sun's longitude and the moon's phases.

Chinese Calendar from Wikipedia, the free encyclopedia.

The Chinese Calendar. History and information from Calendars through the Ages.

Chinese Calendar. A lunisolar calendar, is formed on the movement of the moon. It defines Chinese 24 solar terms, traditional holidays and helps to choose a lucky day before important activities such as marriage proposal, wedding, praying for pregnancy, traveling. Site includes: Chinese Calendar 24 Solar Terms, Customs Concerning the Solar Terms, Heavenly Stems & Earthly Branches, Chinese 60-Year Calendar Circle.
See also The 12 Animals of the Chinese Zodiac with background information and legend about the twelve animals: Rat Ox Tiger Hare Dragon Snake Horse Sheep Monkey Rooster Dog Boar (Pig).

The Chinese Calendar. Learn how the ancient Chinese calculated time using the sun, the moon, and oracle bones. Years were also counted from a succession of eras established by reigning emperors.

Chinese Calendar from Wikipedia. Includes: Relation between moon phases and dates, Solar year and solar term, Relations between solar terms and months, Age recognition in China, Year number system, Phenology, Chinese Holidays, History of Chinese Lunar Calendar: Earlier Chinese calendars, Ancient Chinese calendars, Modern Chinese calendars.

Chinese New Year Calendar. There are 3 ways to name a Chinese year: By an Animal, By its Formal Name (Stem-Branch), or By Current Year (e.g. 2016 = Year 4713 by the Chinese Calendar). See also: The Chinese Calendar.

Chinese Zodiac Sign Calculator. Each year of the Chinese calendar is associated with one of the twelve animals of the Chinese Zodiac. Use the form provided to determine the Chinese Zodiac animal for your birth date. Check each Zodiac animal to see your Personality, Health, Career, Relationships, and Compatibility with other animal signs. The 12 Zodiac signs: Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, Pig.

The Christian Calendar from Calendars through the Ages.

Create Calendar for Any Year. Choose a year and a country. Results will show phases of the moon, Holidays and Observances for that country, with option to customize your display.

The Curious History of the Gregorian Calendar - Eleven days that never were by Ben Snowden.

Dating - Calender Years. 1752 was the first year in England to officially begin on 1 January. Until the Calendar Act of 1752, the year in England began officially on 25 March (Lady Day), and not 1 January.

Early Roman Calendar from Calendars through the Ages.

Egyptian calendar from Wikipedia.

The Egyptian Calendar from Calendars through the Ages.

Ethiopian Calendar from Calendars through the Ages.

Free Printable Calendar Templates. Create free printable calendars that are formatted for Microsoft Word®.

Free Printable Calendars. Free calendars from Printfree.com. Print monthly or yearly calendars.
2020 Calendar Template from CalendarLabs. Popular Calendar Template Pages include: Blank Calendar, PDF Calendar, Photo Calendar, Word Calendar, Excel Calendar, Julian Calendar, Family Calendar, Accounting Calendar, Business Calendar, Fiscal Calendar, Monthly Calendar, Quarterly Calendar, Yearly Calendar.
Calendar for Year 2020 (Australia) from Time and Date. Choose a country from A-Z, Australia to Zimbabwe.
Print 2020 Canada Calendar from Calendar Labs. Includes Canada Holidays and Observances.
Calendar for Year 2020 (Canada). Free print calendar from timeanddate.com.
Free Printable Canada 2020 Calendar Template PDF, Excel, Word by yotan, Print Template Calendar.
Calendar for Year 2020 (United Kingdom) from Time and Date.
Calendar for Year 2021 (United Kingdom) from Time and Date.
2020 Calendar - United States from Calendar Date. United States 2020 yearly calendar with Federal Holidays highlighted in red and prominent holidays highlighted in blue.
Calendar for Year 2020 (United States) frin Time and Date. Holidays and Observances: Federal Holidays highlighted in red and prominent holidays highlighted in blue. You can also ADD more holidays/observances: Major Christian, Major Jewish, Major Muslim, Major Hinduism, All Holidays and National/Global Observances, and more.

The French Revolutionary Calendar (or Republican Calendar) from Calendars through the Ages.

Frequently Asked Questions about Calendars. Site answers many FAQ about the calendar, e.g. How does one count years? What is the Roman calendar? How did the Romans number days? What does an Islamic year look like? What is the origin of the 7-day week? What is the Long Count in the Mayan Calendar? Did the Mayas think a year was 365 days?

Future Calendars from Calendars through the Ages.

Gregorian calendar from Wikipedia, the free encyclopedia. The Gregorian calendar or New Style calendar is a 12-month calendar first proposed by the Calabrian doctor Aloysius Lilius to replace the less precise Old Style Julian calendar. Decreed by Pope Gregory XIII on 24 February 1582, the Gregorian calendar is the solar calendar now in use worldwide.

The Indian Calendar from Calendars through the Ages.

The Islamic Calendar from Time and Date. "Muslims around the world use the Islamic calendar to determine the dates of religious events and observances. It is also known as the Hijri calendar or the Muslim calendar. The Hijri calendar is not to be confused with the Solar Hijri calendar used in Iran and Afghanistan."

Islamic calendar from Wikipedia.

The Islamic Calendar from Calendars through the Ages.

The Jewish Calendar from Calendars through the Ages. See also Jewish Calendar Conversions in One Step, Jewish Calendar Description by Stephen P. Morse.

Julian calendar or Old Style calendar from Wikipedia, the free encyclopedia. "The Julian calendar, a reform of the Roman calendar, was introduced by Julius Caesar in 46 BC, and came into force in 45 BC."

The Mathematics of the Chinese Calendar by Helmer Aslaksen, Department of Mathematics, National University of Singapore.

The Mayan Calendar. History and information from Calendars through the Ages.

Other Ancient Calendars include Babylonian calendar, and Egyptian calendar.

Perpetual Calendar from Infoplease. View any month, any year, in the Gregorian calendar. Enter any year, past or future. Click any day for more information: Equivalent date in Hebrew calendar, Chinese calendar and Islamic calendar, plus This Date in History citing major world events that occurred on this date.

Persian Calendar (Iran) from Calendars through the Ages.

Printable Calendars. Free calendars from Printfree.com. Print monthly or yearly calendars. Free Printable Calendar Templates from printablecalendar.ca. Free Printable Calendars from PrintFree.com. Free Printable Yearly Calendars.

Free printable calendars from CalenWeb. View, download and print more than 200 calendars, diaries and other schedules.

Roman Calendar - Early Roman Calendar. History and information from Calendars through the Ages.

The Shire Calendar. "The calendar used by the Hobbits of the Shire divided the year into twelve months which, unlike the irregular months of Roman and modern Europe, were of equal length: every month in the Hobbit year had exactly thirty days."

Timeline of Interesting Calendar Facts from Calendars through the Ages.

Western-Chinese Calendar Converter. Convert between Solar and Lunar Calendars.

Daylight Saving Time

Daylight Saving Time. Learn about history of daylight saving, standardization of time, and when regions around the globe spring ahead and fall back, from WebExhibits.org.

Daylight Saving Time 2018: A Guide to the When, Why, What and How by Jeanna Bryner, Live Science Managing Editor, March 9, 2018.

Daylight saving time from Wikipedia, the free encyclopedia.

Daylight Saving Time Around the World from Time and Date. A-Z List of Countries Observing DST Clock Change Events 2017 as well as Countries that Do Not Observe DST: from Afghanistan to Zimbabwe.

Daylight Saving Time in Canada. In 2007, Daylight Saving Time begins on the second Sunday in March and ends on the first Sunday in November. This pattern will be followed by all provinces which observe daylight saving time and each province has amended their legislation to reflect this change. (Previously, Canada had observed Daylight Saving Time from the first Sunday in April until the last Sunday in October). This change in Daylight Saving Time will keep Canada's Daylight Saving Time pattern consistent with the United States.

Daylight Saving Time Statistics from Time and Date. Statistical and historical overview of Daylight Saving Time (DST), including use per continent, number of countries using DST, and a list of past and present DST use worldwide.

Daylight Time. When does Daylight Time begin and end in the United States? Starting in 2007, daylight time begins in the United States on the second Sunday in March and ends on the first Sunday in November. On the second Sunday in March, clocks are set ahead one hour at 2:00 a.m. local standard time, which becomes 3:00 a.m. local daylight time. On the first Sunday in November, clocks are set back one hour at 2:00 a.m. local daylight time, which becomes 1:00 a.m. local standard time. Not all places in the U.S. observe daylight time, e.g. Arizona, Hawaii, and most of Indiana do not use it. Site includes a link to Energy Policy Act of 2005.

Did Ben Franklin Invent Daylight Saving Time? from the Franklin Institute. "Daylight saving time is one thing that Franklin did not invent. He merely suggested Parisians change their sleep schedules to save money on candles and lamp oil ... So who did first propose daylight saving time? We can place the blame on a New Zealand entomologist, George Hudson, who wanted more daylight in the evenings and presented the idea in 1895."

Does Daylight Saving Time Conserve Energy? By Charles Q. Choi, Scientific American. Recent studies shed some light on the efficiency of seasonally changing the clocks.
See also: Daylight saving time: The myths and the truths by Michael Pearson, CNN, October 18, 2017. Includes video.

History of Daylight Saving Time - DST from timeanddate.com. Daylight Saving Time (DST) is used to save energy and make better use of daylight. It was first used in 1908 in Thunder Bay, Canada. See also: United States and Canada: Daylight Saving Time Extended Starting 2007 from timeanddate.com.

History and Science of Time

The Last Wishes of Alexander the Great:
On his death bed, Alexander summoned his generals and told them his three ultimate wishes:
1. The best doctors should carry his coffin;
2. The wealth he has accumulated (money, gold, precious stones) should be scattered along the procession to the cemetery.
3. His hands should be let loose, hanging outside the coffin for all to see!!

One of his generals who was surprised by these unusual requests asked Alexander to explain.
Here is what Alexander the Great had to say:
1. I want the best doctors to carry my coffin to demonstrate that, in the face of death, even the best doctors in the world have no power to heal;
2. I want the road to be covered with my treasure so that everybody sees that material wealth acquired on earth, stays on earth.
3. I want my hands to swing in the wind, so that people understand that we come to this world empty handed and we leave this world empty handed after the most precious treasure of all is exhausted and that is TIME.
4. We do not take to our grave any material wealth. TIME is our most precious treasure because it is LIMITED. We can produce more wealth, but we cannot produce more time.
5. When we give someone our TIME, we actually give a portion of our life that we will never take back. Our TIME is our life!
6. The best present that you can give to your family and friends is your TIME.

May you be granted plenty of TIME, and may you have the wisdom to give it away so that you can LIVE, LOVE and DIE in peace.

~ The above is a variation of quotes about Death by Alexander the Great. Email received 16 Nov. 2013. Source unknown.

Alexander III of Macedon (20/21 July 356 BC - 10/11 June 323 BC), commonly known as Alexander the Great. ~ Wikipedia.
See: Was Alexander the Great Pronounced Dead Prematurely? By Jason Daley, Smart News, smithsonian.com, February 5, 2019.

A brief history of telling time from The Conversation. Sundials and water clocks. Atoms and lasers. See also: How an atomic clock works, and its use in the global positioning system (GPS). YouTube video, 4:32 min. Published on Jun 12, 2012 by engineerguy.

Anthill 1: About time, The Conversation UK's inaugural podcast. Listen to this audio, 34:11 min. In a brief history of telling time, physicist Kenneth Grattan speaks about how humans perfected the measurement of time, from sundials to atomic clocks. Historian Richard Evans explains how time zones were created, and computer scientist Markus Kuhn tells us why the world would be in a spin without leap seconds.

A Brief History of Time from the Big Bang to Black Holes by Stephen Hawking
A Brief History of Time
from the Big Bang
to Black Holes
by Stephen Hawking
        A Brief History of Time by Stephen Hawking
A Brief
of Time
by Stephen Hawking
      A Briefer History of Time: The Science Classic Made More Accessible
A Briefer History of Time:
The Science Classic
Made More Accessible
by Stepxhen Hawking

Stephen Hawking dies aged 76 from BBC News. "The British physicist was known for his work with black holes and relativity, and wrote several popular science books including A Brief History of Time. At the age of 22 Stephen Hawking was given only a few years to live after being diagnosed with a rare form of motor neurone disease. The illness left him wheelchair-bound and largely unable to speak except through a voice synthesiser." See: Obituary. Stephen Hawking was born on 8 January 1942 in Oxford, England and died on 14 March 2018 at his home in Cambridge, England.

Award-winning scientist Stephen Hawking dies at 76 by Karma Allen, ABC News, Mar 14, 2018.

Stephen Hawking dead at 76 from Associated Press, Mar 14, 2018. "The best-known theoretical physicist of his time, Hawking wrote so lucidly of the mysteries of space, time and black holes that his book, A Brief History of Time, became an international bestseller, making him one of science's biggest celebrities since Albert Einstein.

Even though his body was attacked by Amyotrophic Lateral Sclerosis, or ALS (also known as Lou Gehrig's disease, or motor neuron disease), when Hawking was 21, he stunned doctors by living with the normally fatal illness for more than 50 years. A severe attack of pneumonia in 1985 left him breathing through a tube, forcing him to communicate through an electronic voice synthesizer that gave him his distinctive robotic monotone ..."

https://www.thesun.co.uk/news/5232508/from-killer-robots-to-donald-trump-five-ways-stephen-hawking-has-predicted-the-world-will-end/ APOCALYPSE HOW? From killer robots to Donald Trump, five ways Stephen Hawking has predicted the world will end. The world famous physicist says we must act now to prevent our extinction. By Jay Akbar, 29 Dec 2017 What do robots, nuclear and Donald Trump have in common? Photo credits: PA/Press Association
Stephen Hawking
Photo credits: PA / Press Association
From article:
Apocalypse How? by Jay Akbar, The Sun, 29 Dec. 2017

A Brief History of Time. YouTube video, 2 hrs. 48 min. 38 sec. "A Brief History of Time (subtitled 'From the Big Bang to Black Holes') is a popular-science book written by British physicist Stephen Hawking and first published by the Bantam Dell Publishing Group in 1988." ~ Wikipedia. Sound of Full Book. Explaining 14 billion years of existence in less than 3 hours.

A Brief History of Time from Wikipedia. "A Brief History of Time: From the Big Bang to Black Holes is a popular-science book on cosmology (the study of the universe) by British physicist Stephen Hawking. It was first published in 1988. Hawking wrote the book for nonspecialist readers with no prior knowledge of scientific theories." Stephen Hawking's email: S.W.Hawking@damtp.cam.ac.UK (circa 2011).

Measuring Time by American physicist, Dr. David Lewis Anderson. YouTube video, 2:49 min. Published on May 19, 2010 by TimeResearch.

An entire history of time measurement in six minutes. YouTube video, 6:38 min. Discussion on the history of time measurement in the world and how it preceded every major thought revolution in physics.

The edge of the Universe by Ken Tapping, 26 Sep. 2017. Ken Tapping is an astronomer with the National Research Council's Dominion Radio Astrophysical Observatory, Penticton, BC, V2A 6J9. "The universe began about 14 billion years ago in an event that is called the 'Big Bang' ... 'Big Bang' was a derisive term used by astrophysicist Fred Hoyle, who did not believe it. The term stuck.
The idea that the universe had a definite Beginning comes from the discovery that the universe is expanding. By measuring the distances of galaxies and the speeds they are moving away from us, we can track back where those galaxies were in the past, and we found that just under 14 billion years ago they were all at the same location.
... The Beginning of the Universe was not just a creation of matter and energy; it was also the creation of space and time."

What Caused the Big Bang?

The Beginning of Everything -- The Big Bang YouTube video, 5:54 min. Published on Mar 3, 2014 by Kurzgesagt - In a Nutshell. "Has the universe a beginning or was it here since forever? Well, evidence suggests that there was indeed a starting point to this universe we are part of right now. But how can this be? How can something come from nothing? And what about time?"

The History of Earth - How Our Planet Formed - Full Documentary HD YouTube video, 1 hr 31:51 min. Published by Wisdom Land, Dec 11, 2016. "It is theorized that the true age of the earth is about 4.6 billion years old, formed at about the same time as the rest of our solar system. The oldest rocks geologists have been able to find are 3.9 billion years old. Using radiometric dating methods to determine the age of rocks means scientists have to rely on when the rock was initially formed. In the infancy of our home planet the entire earth was molten rock - a magma ocean."

Telling Time and the Age of the Universe by David C. Black, Director of Lunar and Planetary Institute (LPI). "It is the issue of age, and how we determine the passage of time, that is the subject of this article." See also How Old Is the Universe? "Until recently, astronomers estimated that the Big Bang occurred between 12 and 14 billion years ago. To put this in perspective, the Solar System is thought to be 4.5 billion years old and humans have existed as a genus for only a few million years. Astronomers estimate the age of the universe in two ways: 1) by looking for the oldest stars; and 2) by measuring the rate of expansion of the universe and extrapolating back to the Big Bang ..."

How Do We Know the Age of the Universe? YouTube video, 5:42 min. Published on Feb 20, 2018 by SciShow Space.

Geological history of Earth from Wikipedia. Science Engineering and Technology Timeline from Intute - predecessor sites (EEVL, GEsource and PSIgate) together make up Intute. Web Geological Time Machine and History of Geologic Time Scale. The Geologic Time Scale in Historical Perspective from University of California Museum of Paleontology (UCMP). What do the divisions of the geologic time scale signify?

A Guide to Metric Time or Decimalized Time. Metric Time (MT) is an attempt to create a decimalized time system for our modern base-10 using world.

History of Telling Time - A brief history of time. Talking Clock - Clock shows exact time as of now; click to hear what time it is. (Be patient, slow loading as it figures out where you are in the world). Timeline of Time, Types of Clocks - Sun clocks, Water clocks, Mechanical clocks, Quartz Clocks, Atomic Clocks, Time Zone Information, United States Time Zones, Map of World Time Zones, Telling Time Games & Quizzes, Interactive Teaching Clock, Printable Paper Clock, Telling Time Activities: How old are you in weeks, hours, minutes, seconds? How far away is your next birthday? Time Glossary, plus Lessons and Worksheets for Teachers.

History of Time Measurement. YouTube video, 8:21 min. Dr. Benjamin Baker and Chantal Klingbeil discuss the manner in which time has been measured throughout history. What people have used through history to measure time: water, candle, sundials, sun, stars, mechanical clocks, atomic clocks, etc.

Horologium: Calculating the Hours in Ancient Rome. How the Romans measured time: Hours, Days, Seasons (Winter Solstice and Summer Solstice).

Horology from Wikipedia, the free encyclopedia. Horology is the study of the science and art of timekeeping devices. Clocks, watches, and marine chronometers are examples of instruments used to measure time.

Hour from Wikipedia, the free encyclopedia. Definition: In modern usage, an hour is a unit of time 60 minutes, or 3,600 seconds in length. History. Different ways of counting hours.

How Time Works. Time cannot be seen or sensed. It just happens. Human beings have therefore created ways to measure time that are totally arbitrary. Topics include time's origins, some common time spans, clocks, time zones, daylight-saving time, calendar, B.C. and A.D.

Intellectual history of time from Wikipedia, the free encyclopedia.

Measuring Time. YouTube video, 2:49 min. A short video that provides a brief overview of man's quest to develop new and better ways to measure time. An excerpt from documentary "Time Travel - Journeys into Time" written and hosted by American physicist, Dr. David Lewis Anderson.

Sir Sandford Fleming (1827-1915) - Father of Standard Time. Standard Time was invented by Scottish Canadian, Sir Sandford Fleming in 1878. Article by Mary Bellis, an inventor. From Inventors.About.com.

Space-Time and the Speed of Light | Einstein's Relativity. YouTube video, 5:43 min. "In physics, spacetime (or space-time) is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space being three-dimensional and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions."

Time from Wikipedia, the free encyclopedia. Time Measurement: history and devices, Definitions and standards: World time, Sidereal time, Chronology, Time in religion and mythology, Linear and cyclical time, Time in philosophy, Time as "unreal", Nature of time in physical sciences, Time in classical mechanics, Time in modern physics, Spacetime, Time dilation, Arrow of time, Quantised time, Time and the Big Bang, Time travel in science fiction, Use of time, and more.

A Walk through Time. The Evolution of Time Measurement. Topics covered: Ancient Calendars, Early Clocks, Revolution in Timekeeping, The "Atomic Age", World Time, Scales, National Institute of Standards and Technology (NIST) Time Calibration.

Leap Year

The History of Leap Year - Who Invented Leap Year? From Mary Bellis, About.com.

Leap year from Wikipedia, the free encyclopedia.

Leap Year. A leap year is a year in which an extra day in added to the calendar in order to synchronize it with the seasons. Find out more about the Leap Year, from Eric Weisstein's World of Astronomy.

Leap Year as explained by Newton, Ask a Scientist, from Forest Preserve District of Cook County (Illinois).

Leap Year. Fun facts from Care2.com. History of Leap Year. February 29th is also known as Sadie Hawkins Day. Developed out of the popular cartoon strip "Li' Abner" by Al Capp, when unmarried women could run after unmarried men to propose on Sadie Hawkins Day. The tradition actually started with St. Patrick and St. Bridget (5th Century) in Ireland.

Leap Year Calculator from Online Conversion.

Leap Year Traditions from Sheri & Bob Stritof, About.com. Leap Year has been the traditional time that women can propose marriage. St. Bridget's Complaint - It is believed this tradition was started in 5th century Ireland when St. Bridget complained to St. Patrick about women having to wait for so long for a man to propose.

Leap Year Rules from Western Washington University (WWU) Planetarium. Leap Year Explained from infoplease.

Leap Years & Leap Seconds from NIST Time and Frequency FAQ. What is a leap year? What is a leap second? Why do we need leap seconds?

Why is February only 28 days long? By Scripps News Staff, Feb 15, 2023. The Romans dedicated the month to the God of purification and left it with an even 28 days. February would then be moved after January in 452 B.C.

Why are leap years used? From time and date.com.

Lesson Plans on Time

Clock Face Generator from Helping With Math. See also other Math Worksheet Generators.

Eyes on the Sky, Feet on the Ground: Chapter Three - Time and the Calendar from Harvard-Smithsonian Center for Astrophysics. Discussions to follow student activities. Materials listed, how-to-make directions provided.
● Topic 1 - Recording the Passage of Time Activities: How to make Hour Glass or Sand Clock, Water Clock, Candle Clock, Atomic Clock.
● Topic 2 - Time Zones Activities: What Time Is It? Daylight Saving Time.
● Topic 3 - The Moon: A Natural Calendar Activities: Make a Lunar Calendar.
● Topic 4 - The Zodiac Activities: Sun's Yearly Trip Though the Zodiac, Hi! What's Your Sign? Precession of the Earth's Axis.
● Topic 5 - The History of the Calendar Activities: Exploring the Calendar, Make Personalized Calendars.
● Topic 6 - Future Calendars Activity: Invent a New Calendar.

Local Time & Time Zones

12-hour clock from Wikipedia, the free encyclopedia. The Latin abbreviations "a.m." and "p.m." (often written "am" and "pm"; "AM" and "PM"; and "A.M." and "P.M.") are used in English and Spanish ... In the United States ... since the 1980s, noon is often called 12:00 p.m. and midnight 12:00 a.m., as at the beginning of a day ... but there is sufficient confusion over these uses to make it advisable to use 12 noon and 12 midnight where clarity is required.

Any Time, Anywhere. Correct, current, local time from World Time Server. Check out Time Converter. Set a time from your choice of location to see what time it is at another location in the world.

New York

Get Current Time with World Time Server
world time server Enter a country or city:

Right now, the official U.S. time is: ... time in hours, minutes, seconds, plus today's date, accurate within 0.2 seconds. The Official U.S. Time for all states. Click on a time zone across a map of the United States, site will instantly provide you with today's date, the current time ticking away, and accurate within 0.3 seconds. Includes links to Time Exhibits.
Time.is. YOUR TIME RIGHT NOW! Time.is - exact time, any time zone. 7 million locations, 46 languages, synchronized with atomic clock time. My clock is 4.8 seconds behind. Accuracy of synchronization was ±0.101 seconds. Time in Fredericton, New Brunswick, Canada now: 19:05:04 Wednesday, February 6, 2019, week 6 Sun: ↑ 07:41 ↓ 17:40 (9h 9m) More info...
Beijing - 07:05, Moscow - 02:05, Paris - 00:05, London - 23:05, New York - 18:05, Toronto - 18:05, Vancouver - 15:05.
● See also: The Time Now: Eastern Daylight Time (EDT)

Frequently Asked Questions (FAQ) from National Institute of Standards and Technology (NIST), Time and Frequency Division. Are noon and midnight 12 a.m. or 12 p.m.? Why is UTC used as the acronym for Coordinated Universal Time? What is a Modified Julian Date (MJD)?

Local Times Around the World. First, select a continent or region: Africa, America, Antarctica, Asia, Atlantic, Australia, Europe, or Pacific. Then choose a country and a location to view details.

Clock Face Generator from Helping With Math. See other Math Worksheet Generators.

Military/NATO/Letter Time Zones. Z - Zulu time - Zero meridian time.

Offset Time Zones by Matt Rosenberg, a professional geographer. Many places in the world use offset time zones. These time zones are offset by a half-hour or even fifteen minutes off of the standard twenty four time zones of the world.

Online Current Time. Set new alarm. Alarm Clock. Timer. Stopwatch. Countdown.

Poodwaddle Time - World Clock showing current date and time for New York, London, Moscow and Tokyo. Also available: Current date and time for around the world cities from A-Z (from Abidjan, Côte d'Ivoire to Zurich, Switzerland).

Time and Frequency Division of the National Institute of Standards and Technology (NIST). Find the Official United States Time. You can set your computer clock to the correct time right now by using the Internet or the Telephone.

Time Genie. What Is the Current World Time? Select a location to see the current time, today's date, time zone, Standard Time difference compared to UTC/GMT, Daylight Saving Time if applicable, Latitude, Longitude, 4 digit city code, e.g. cyyz for Toronto, Canada, plus flag of the country.
Your Clock allows you to compare up to 14 different times around the world.
Future Time allows you to determine what time it will be in various locations at a time in the future.
Time Zone Abbreviations.
Time Zone Converter – Time Difference Calculator.
World Time gives you the Current Time for 133 Cities Around the World.
Random Time gives you the Current Time for 150 World Cities, and each time this page is reloaded, 150 cities, towns or villages will appear in a random fashion.

Time in Canada from Wikipedia, the free encyclopedia. Zones: Pacific Standard Time, Mountain Standard Time, Central Standard Time, Eastern Standard Time, Atlantic Standard Time, Newfoundland Standard Time, Daylight saving time, TZ zones.

Time Zone Abbreviations from Time and Date.com. Includes Time zone tools and information, Calendars, holidays and date calculators, Calendars and Countdown counters.

Standard abbreviations:
● UT = Universal Time
● UTC = Coordinated Universal Time
● GMT = Greenwich Mean Time (used in Europe)
● AST = Atlantic Standard Time (used in U.S. and Canada)
● ET = Eastern Time (used in U.S. and Canada)
● ACDT = Australian Central Daylight Time Military/NATO/Letter time zones:
● Z Zulu Time Zone (Zero meridian time) = UTC
● A Alpha Time Zone = UTC + 1 hour
● B Bravo Time Zone = UTC + 2 hours
● C Charlie Time Zone = UTC + 3 hours
● D Delta Time Zone = UTC + 4 hours
● E Echo Time Zone = UTC + 5 hour
● F Foxtrot Time Zone = UTC + 6 hour
● G Golf Time Zone = UTC + 7 hour
● H Hotel Time Zone = UTC + 8 hour
● I India Time Zone = UTC + 9 hour
● K Kilo Time Zone = UTC + 10 hour
● L Lima Time Zone = UTC + 11 hour
● M Mike Time Zone = UTC + 12 hour
● N November Time Zone = UTC - 1 hour
● O Oscar Time Zone = UTC - 2 hour
● P Papa Time Zone = UTC - 3 hour
● Q Quebec Time Zone = UTC - 4 hour
● R Romeo Time Zone = UTC - 5 hour
● S Sierra Time Zone = UTC - 6 hour
● T Tango Time Zone = UTC - 7 hour
● U Uniform Time Zone = UTC - 8 hour
● V Victor Time Zone = UTC - 9 hour
● W Whiskey Time Zone = UTC - 10 hour
● X X-ray Time Zone = UTC - 11 hour
● Y Yankee Time Zone = UTC - 12 hour

Time Zone Converter. Indicates the current time as you access the site. Apart from allowing you to convert time zones in current time, amazingly, this site allows you to specify a given date and time to convert past or future times. Select a location "From Time Zone" and convert "To Time Zone" of another location. How to Use the Time Zone Converter.

Time Zones in Australia.

Time Zones in Europe.

Time Zones in North America.

US Naval Observatory Master Clock Time.

What Time Is It?. See clock display of time right now where you are. USNO Time in Standard Time Zones. USNO Master Clock Animated GIF Clocks.

Current local times in capitals around the world. A-Z Listing by Country followed by its Capital City, from World Time Zone. Time mode: 24 hours or 12 hours (AM/PM), Sort by city name, Sort by Country, Sort by Time Zone. (Good place to learn capital cities of countries).

Telephone talking clock. Voice announcements of Eastern Time are made at ten-second intervals, followed by a tone whose beginning indicates the exact time. This service is available to the general public by dialling the Ottawa telephone numbers 1-613-745-1576. The time signal also "ticks" each second to facilitate accurate counting down for setting digital chronometers. Three announcements are given, and the caller is then disconnected.

Web clock (Official times across Canada) from National Research Council Canada, Government of Canada.

World Time Server.com. Find current time and date anywhere in the world. Search a location by country or by major city.

Enter a country or city:

Why Has Date Changed for Start of Spring? By Joe Rao, Space.com. The first day of spring no longer falls on March 21. In 2008, spring season starts one day earlier on March 20 in all time zones in North America. In the years 2008 and 2012, those living in Alaska, Hawaii and the Pacific, Mountain and Central time zones will see spring begin even earlier: on March 19. And in 2016, it will start on March 19 for the entire United States (and most likely for Canada as well).

The World Clock - Time Zones - Current Local Times Around the World. You can sort the list of cities around the globe by City, by Country, or by Time Zones. Includes links to Countdown to New Year, Time Zone abbreviations, Generate a Calendar of any Year of your choice, and more.

World Time - 36 time zones at a glance. See also Countries and Time Zones and Astronomical Background. Available in German and English.

World Time Zone from World Time Zone.
World Time Zone Map with current time (24 hour format) from World Time Zone. You have an option to change time mode to 12 hours (AM/PM).
Time zone from Wikipedia.
The World's Time Zones from Reference.com.
World Time Zone Map. Time Zones of All Countries.
Expanded World Time Zone Map from TimeTemperature.com. Or select to view Time Zone separately for each of the following: World | Africa | Asia | Australia | Canada | Caribbean | Central America | Europe | Mexico | Middle East | South America | United States.
World Time Zones by Country.
Time Zone Abbreviations - Worldwide List. Time Zone names, codes and abbreviations for Standard Time and Daylight Saving Time (DST) around the world.

Measuring Time - Clocks

Antique Clocks Identification and Price Guide. Browse more than 38,769 photos and descriptions of antique clocks sold at auction.

Astrolabe from Wikipedia, the free encyclopedia.

Astrolabe History by Karen Meech, Institute for Astronomy, University of Hawaii, Apr 18, 2000. "An astrolabe is a two-dimensional model of the celestial sphere. The name has its origins from the Greek words astron and lambanien meaning "the one who catches the heavenly bodies. An astrolabe is an instrument that once was the most used, multipurpose astronomical instrument.. See also Front and back views of an ancient Arab astrolabe.

Astronomical clock from Wikipedia, the free encyclopedia.

At Home Astronomy: Making a Simple Astrolabe, Using a Simple Astrolabe

Atomic Clock. YouTube video, 2:27 min. From Russia: "The accuracy of time measurement is one of the major problems throughout the whole history of mankind. As the technology developed, the requirements for clock accuracy grew. Clocks have passed a long way of evolution: sundial, water, sand, mechanical, quartz, and finally, atomic. Atomic, or as it is sometimes called molecular or quantum, clock is a device for measuring time, which uses the natural oscillations of atoms or molecules as a batch process. Atomic clocks have the greatest importance for navigation. Determining positions of spacecrafts, satellites, ballistic missiles, aircrafts, submarines, and vehicular traffic in an automatic mode using satellite communication (GPS, GLONASS) are unthinkable without the atomic clock."

China to launch world's first 'cold' atomic clock in space ... and it'll stay accurate for a billion years by Stephen Chen, South China Morning Post, Sep 15, 2016. "And fittingly, the challenge is coming from the country that invented the mechanical clock almost 1,300 years ago - China.
The US clock (the NIST-F2 atomic clock operated by America's National Institute of Standards and Technology in Boulder, Colorado) is a large, heavy machine, standing more than 2.5 metres high, with support facilities filling an entire room, but it is so accurate that it would lose just one second in 300 million years.
In contrast, the Cold Atomic Clock in Space (Cacs) recently developed by researchers in Shanghai can easily be lifted by two people and would fit comfortably in the boot of a car. But it is expected to be three times more accurate than NIST-F2, losing only a second in one billion years."

Our New Atomic Clock Is So Precise That We Need a Better Understanding of Gravity To Use It by Avery Thompson, Popular Mechanics, Nov 30, 2018. Our measurements of gravity are not good enough for NIST's new atomic clock.

This New Atomic Clock Is So Precise Our Ability to Measure Gravity Constrains Its Accuracy by Daniel Oberhaus, Motherboard, TIME, Nov 30 2018. NIST's new atomic clocks will help create the world's most precise map of how Earth's gravity warps spacetime.

These atomic clocks are so precise they can measure the distortion of space-time by science reporter Belinda Smith, ABC Science, 28 November 2018. "These clocks are so accurate they'd lose just half a second if they lasted the age of the universe. That's 14 billion years ... the clocks could tell us what's going on inside the earth by precisely mapping our planet's bumps and lumps ...
Study co-author Will McGrew, a PhD student at the National Institute of Standards and Technology in the US, said the clocks' 'ticking' is produced by oscillations of radiation emitted when electrons in ytterbium atoms are excited by lasers.
It turns out they tick, in almost perfect synchronicity, 500 trillion times a second.
'Measuring time and frequency with such an incredible accuracy provides a really powerful lens to view the natural world,' Mr McGrew said."

Super-accurate atomic clock used in real world for first time from NewScientist.com, Daily News, 12 Feb 2018.

Atomic ticker clocks up 50 years from BBC News. The first atomic clock, which uses the resonance frequencies of atoms to keep extremely precise time, was developed by Dr Louis Essen at UK's National Physical Laboratory in 1953. By 1964, Essen had reduced the timekeeping errors from one second in 300 years to about one second in 2000 years. See also biography of Louis Essen and Atomic clock from Wikipedia, the free encyclopedia.

Brief History of Atomic Clocks at NIST. Timeline of Atomic Clock History at National Institute of Standards and Technology.

A Brief History of Clocks and Calendars by Tim Lambert. Includes Early Clocks, Mechanical Clocks, and Calendars Through the Ages. See also Clocks History | A brief history of clocks by tomhre, Clocks and Chimes from Tom Harris.

A Brief History of Time Measurement by Leo Rogers, from NRICH enriching mathematics. "Prehistoric people first recorded the phases of the Moon some 30,000 years ago, and recording time has been a way by which humanity has observed the heavens and represented the progress of civilization." Natural Events, Measuring time by the Sun, the Moon and the Stars, Precession, Inventions for measuring and regulating time: Oil Lamps, Candle Clocks, Water Clocks, Hour Glasses or Sandglasses, The Division of the Day and the Length of the 'Hour': The Merkhet, Earliest Mechanical Clock, More Accurate Mechanical Clocks.

Explore Clocks, Nails, and More! Google image from https://www.pinterest.ca/pin/109634572155876059/9Oct17
Photo source: Unusual Facts

Cesium Fountain Atomic Clock - The Primary Time and Frequency Standard for the United States. From National Institute of Standards & Technology (NIST).

Clock from Wikipedia, the free encyclopedia. Contents include: History (Water clocks, Early mechanical clocks, Early astronomical clocks), Types of Clocks (Analog clocks, Digital clocks, Auditory clocks, Timekeeping methods), Purposes of Clocks (Ideal clocks, Navigation), Specific types of clocks (Alarm clock, Atomic clock, Balloon clock, Cuckoo clock, Hourglass, Japanese clock, Lantern clock, Pendulum clock, Railroad chronometers, Skeleton clock, Stopwatch, Sundial, Tide clock, Watch, Water clock, and many more).

Clock History: An Introduction from Mystical World Wide Web. Contents include: Ancient Calendars, Clocks, Sun Clocks, Water Clocks, Europe and Clocks, Mechanical Clocks, Quartz Clocks, Atomic Clocks, and Time Out.

Clock Museum, Vienna, Austria. A small museum filled with over 1,000 clocks, and one particular clock calibrated to run until the year 9999 - Description and review from Atlas Obscura. "The Viennese Clock Museum is housed in the Harfenhaus (Harpist's House), one of the oldest homes in Vienna. With around 1,000 clocks in the 'Uhrenmuseum,' there is much to see.

Of particular note is the 230-year-old astronomical clock, constructed by an Augustinian friar. Built in 1679, and calibrated up to the year 9999, it is a gorgeous piece of engineering. With layers upon layers of golden gears, and over 30 readings and dials, it is stunning. Each hand takes 20,000 years to revolve.

It's all arranged in chronological order, from ornate pocket watches, to a 15th-century tower clock, to sundials, to rare Japanese pillar clocks, to grandfather clocks, to Black Forest cuckoo clocks, to a huge clock organ."

Clock Museum - Uhrenmuseum from Vienna Now - Forever. Address: Schulhof 2, 1010 Wien. Prices: General admission: €7. Discounted rate: €5. Young people under 19: €0. 1st Sunday of the month: Free admission for all. Seeing eye dogs allowed. Exhibits on three floors.

Wien Museum: Uhrenmuseum auf Deutsch, in German.

Uhrenmuseum - Clock Museum in English. Collection of Clocks and Watches (Uhrenmuseum). Includes photo gallery and a leaflet to download.
"Journey through time to a place where everything runs like clockwork. A unique gem in the heart of the city, the Clock Museum presides over one of the most significant collections of time pieces in Europe. Seven hundred clocks from around the globe mark time in an enchanting Old Viennese building. Spread over three floors, the exhibition tells a story of scientific advances and technological precision, but also of social transformation and design trends in the decorative arts."

Clock Museum (Uhrenmuseum), Vienna, Austria. Trip Advisor reviews.

Clocks by Ellie Crystal. Illustrated. Article covers history of clocks - Sumerians were one of the first ancient people to use sundials by dividing the day into 12 parts and each part about 2 hours long, Egyptians also divided the day into 12 parts and used huge granite columns called Cleopatra Needles (obelisks) to keep track of time periods, Early water clock, Su Sung water clock tower, Hour glass, Modern clocks, Pendulum clocks, Quartz clock, Atomic clocks, Candle was once used as an 'Alarm Clock', and other interesting information.

Clocks and Calendar History by Mary Bellis, an inventor. From Inventors.About.com.

Clocks and Watches - Images from New York Public Library Digital Gallery. Images may be enlarged for viewing.

How to Teach Kids to Tell Time from WikiHow.

What time is it? From sundials to atomic clocks from Institute of Mathematics, UK. PDF Version

The Canadian Clock Museum Virtual Tour. View images of Midgets Palace "grandfather" clock, Woodstock model (1 of 7 wall clocks made by Arthur Pequegnat Clock Company), a unique animated grandfather clock made in 1980s by Canadian craftsman Werner Friedrich, examples of Seth Thomas (Plymouth Hollow, Connecticut) 30-hour and 8-day clocks sold door-to-door in Canada West in the 1850s-1860s by various clock pedlars, and many other unusual clocks.

Cuckoo clock from Wikipedia.
Schneider Clocks or Cuckoo Clocks from Anton Schneider Söhne, Kuckucksuhrenfabrik, Schwarzwälder Uhren.
Schneider Clocks or Cuckoo Clocks from Anton Schneider Söhne, Kuckucksuhrenfabrik, Schwarzwälder Uhren.
The Cuckoo Experience. Crafted by hand, made by the heart. The story of Schneider and the art of cuckoo clocks.
How a cuckoo-clock is born. (Auf Deutsch). Video, 4:43 min.
Cuckoo-Palace. Anton Schneider German Cuckoo clocks - cuckoo clock. "Anton Schneider first began producing his world famous cuckoo clocks in a farmhouse in Schonach, Black Forest in 1848. For over a century, the Anton Schneider name has been linked to the highest quality and most beautiful cuckoo clocks in all the world."

The Development of the Clock and the Concept of Time in the Middle Ages . Examples of some clocks and time keeping instruments typical of the Middle Ages, e.g. Pocket dial, Astrolabe, and Water clock. See also the making of a Canterbury Dial and other Replica Instruments including an automatic water clock.

Did Humans Create Time? From Debate.org. "Time is imposed upon the seasons. Humans created time - Seconds, Minutes, Hours, Days, Weeks, Months, Years. Centuries and beyond. These are human inventions. A way to organize everything." "No humans did not create time. Humans gave time a name and place, but they did not create time."

Exact Time. Click here to see this very instant the exact time on the US Naval Observatory Master Clock. See also exact Universal Time, Eastern Standard Time, Central Standard Time, Mountain Standard Time, Pacific Standard Time, Alaska Standard Time, and Hawaii-Aleutian Standard Time.

Galileo: The Best Atomic Clock in Space. YouTube video, 2:55 min. How the Galileo Atomic Clocks Work. "The Galileo satellites will carry two types of clocks: rubidium atomic frequency standards and passive hydrogen masers. The stability of the rubidium clock is so good that it would lose only three seconds in one million years, while the passive hydrogen maser is even more stable and it would lose only one second in three million years."

Hourglass from Wikipedia, the free encyclopedia.

How an atomic clock works, and its use in the global positioning system (GPS). YouTube video, 4:33 min. "Bill shows the world's smallest atomic clock and then describes how the first one made in the 1950s worked. He describes in detail the use of cesium vapor to create a feedback or control loop to control a quartz oscillator. He highlights the importance of atomic team by describing briefly how a GPS receiver uses four satellites to find its position."

How Atomic Clocks Work from howstuffworks. How is Atomic Time Measured? Are Atomic Clocks Radioactive? What Are the Types of Atomic Clocks? How Does a Practical Cesium Atomic Clock Work? and When Was the Atomic Clock Invented?

How Digital Clocks Work from howstuffworks. Introduction, The Basics, High-Level View, Building Your Own Digital Clock, Circuit Diagram, 7490 Pinout, Creating the Second Hand, Displaying the Time as Numerals.

How Pendulum Clocks Work from howstuffworks. Pendulum clocks have been used to keep time since 1656. Find out how a pendulum clockworks, as well as the difference between a weight-driven and a spring-driven clock in the Q & A section.

How Quartz Watches Work from howstuffworks. Introduction, Before Quartz, The Quartz Crystal.

How to Build a Grandfather Clock by Brian Adler, eHow. How to Make a Grandfather Clock Chime from eHow.

How to Build a Water Clock from eHow. How to Make a Simple Water Clock from eHow. How to Make an Ancient Egyptian Water Clock from eHow.

How to Construct a Sand Clock by Alicia Bodine, eHow.

How to Make Miniature Wooden Clocks by Karen Frisch, eHow.

How to Read a Clock with Hands by jeansmith99, eHow. How to Read a Clock With 3 Hands by Justin Wash, eHow.

Invention of Clocks: Sun Clocks, Water Clocks, Obelisks - Egyptian shadow clock, Mechanical Pendulum Clocks and Quartz Clocks, Atomic Clocks and Time Standards from Inventors.About.com.

The Leicester Time Trail by Allan Mills. Illustrated. Contents: Astronomical Background, Sundials, Water Clocks, Modern Sundials, Sandglass and Candle Clock, Mechanical Clocks - Verge-and foliot clocks, Pendulum clocks, Automaton clocks, Public clocks, Domestic clocks, Moon dial, and Astronomical clocks.

Marc Tovar's Wooden ClockWorks. Lots of excellent illustrations of wooden clock plans designed for the scroll saw. Patterns are drawn on TurboCad and are very accurate.

Measuring time by setting fire to various things.

Old Father Time from novareinna.com. "Chronos (also known as Chronus) is the personification of time itself. Indeed, the word means 'time' and is the root of 'chronology' and other modern words ... Since ancient history, time has been identified with Saturn.tp"

Time, Clocks and Gears. YouTube video, 8:50 min. "This video resource is designed to support the teaching of gears at an introductory level by explaining the role that gears play in mechanical clocks. Tower clocks, like Big Ben, use an elaborate set of gears to display time. The video includes information about Foliot and Pendulum clock mechanisms."

Time Travel Origins Oldest Clock in World Egyptian Water Clock Earliest Watch Glastonbury Clock. YouTube video, 5:23 min. Good material but video jiggledy.

Toronto Chapter of the National Association of Watch and Clock Collectors. An association of people in Ontario who meet several times each year to share interest in clocks and watches. Meetings consist of a mart, where members share all things horological, by selling or exchanging in a marketplace setting. At each meeting, information is shared about various aspects of this hobby. These include technical subjects relating to watches and clocks, historical information, and personal experiences. Visitors are welcome to the meetings. Contact chapter33@rogers.com.

Visualizing Video Streams Using Sand Glass Metaphor by Edward Chang and Yung-Hsiang Lu, Stanford University. Includes illustrations of a 1896 Clog Almanac with the times of the season changes carved on it, Chinese Water Clock, Candle Clock, Coiled Clock, Insense Clock, Sand Clock, Magic Sand Glass, and more.

Water clock from Wikipedia, the free encyclopedia.

Measuring Time - Sundials

Analemmatic sundials: How to build one and why they work by Chris Sangwin and Chris Budd, Plus Magazine.

Archaeologists Uncover Rare 2,000-year-old Roman Sundial and it Tells Them More than Just the Time from Ancient Origins, 9 Nov. 2017.

The British Sundial Society. Promoting the Art and Science of Gnomonics since 1989. How Sundials Work. The BSS Sundial Glossary. Advice and help on Making Sundials.FAQ.

Building a Sundial by James Henriques, Professor of Physics and Astronomy. Types of Sundials (illustrated): Egyptian Shadow Clock, Human Sundial, Classic Sundial, Bill Nye's Design for Seattle, Ring Style, Wall Sundial, U. of Washington.

Chaldean Sundial, Greece, 320 BCE by Allison Crawford and Lei Liu, Smith College Museum of Ancient Inventions.

Frans Maes Sundial Site. Picture Gallery of some 200 sundials.

Fun in the Sun: A Sundial Tutorial by Helga Nordhoff. Introduction: History of the Sundial, Earth and our Solar System, Types of Sundials: Altitude dials, Azimuth dials, Other sundials, Build your own Sundial, Photos of Sundials in South Africa, A - Z, a glossary of Sundial terms.

How to Make a Sundial from eHow.

How to make a sundial. YouTube video, 3:42 min.

North American Sundial Society. All Things Sundial. New Insights into Ancient Sundials. 13th Century BCE Ancient Egyptian Sundial Discovered. Antique Sundial Treasures.

Six sundial projects for you to make from Sundials on the Internet, UK. See also New Sundials.

Solar Noon Calendar. Print Your Solar Noon Calendar wherever you are in the world. Site provides you with a table showing the exact time of solar noon for your exact location for each day of the year, enabling you to set up your sundial with accuracy.

Sundial from Wikipedia, the free encyclopedia.

Sundials and Astronomical Clocks from Deutsches Museum, Munich, Germany. Courtyard Sundial, Vertical Sundial, Sundial Garden.

Sundials and Latitude. YouTube video, 5:30 min.

Sundials on the Internet. Contents include:
An introduction to sundials and how they work
Six sundial projects for you to make
How to set up a horizontal sundial
Pictures and descriptions of new public sundials from all over the world
The many different types of sundials
The Leicester Time Trail by Allan Mills with illustrations: Astronomical Background, Sundials, Water Clocks, Modern Sundials.

Sundial from Wikipedia, the free encyclopedia.

The Sundial and how to make a sundial, How Do Sundials Work from Yale Scientific, Eestablished in 1894. Building a Simple Sundial, Sundial Construction (in PDF) from Goddard Space Flight Center, NASA.

Sunshine in Your Pocket! Making a sundial for the Northern hemisphere. Choose a level on how to make your own horizontal sundial: Advanced, Intermediate, or Novice. If you are not comfortable using a protractor and are not familiar with the trig functions sine and tangent, you can start at the Novice level. Excellent Website.

When Time Began by Niclas Marie. "Sundials are the oldest known devices that are used to measure time. It depends on the rotation and movement of the sun. As the sun moves from east to west, the shadows formed predict the time of the day. The Egyptians were the first to use the sundials."

Miscellaneous Sites on Time

History of Measurement: Units of Time and Angle from Wikipedia, the free encyclopedia. "We can trace the division of the circle into 360 degrees and the day into hours, minutes, and seconds to the Babylonians who had sexagesimal system of numbers. The 360 degrees may have been related to a year of 360 days."

How time works from howstuffworks. Contents: Introduction to How Time Works, Time's Origins, Clocks, Time Zones, Daylight-saving Time, The Calendar: Years, Months, B.C. and A.D., plus related articles:
How Pendulum Clocks Work
How Digital Clocks Work
How Quartz Watches Work
How Atomic Clocks Work
How Time Travel Works, plus links to:
Time and Date.com
World Time Server
World Clock from The Time Now - A more accessible site for the vision impaired than many other sites.
The World Clock - Time Zones
U.S. Naval Observatory: World Time Zones.

Innovative Ideas to Measure Time in the Year 2023 by Tom Smith, Dec 2022. There are 6 methods used to calculate time: Sundials, Aquatic Clocks, Mechanical Timepieces, Quartz Clocks, Atomic Clocks, and Time Calculators. The first 5 are old time calculation methods. Tom points out that the modern time calculator is a tool that has overwhelmed the limitations faced while calculating time with ancient devices.
See also: Birthday Calculator from 1HappyBirthday. Find out how long you have been alive down to the seconds.
Clock Calculator: Add Time or Subtract Time from TimeandDate.com. Enter a date and time, then add or subtract any number of months, days, hours, or seconds.
Time Duration Calculator from CRM (Customer Relationship Management). Enter Start Time. Enter End Time. This Time Duration Calculator will give you the Time Difference.
Time Calculator from Calculator-Online. Use this calculator to "add" or "subtract" two different time values.
Time Card Calculator from Calculator-Online. This calculator will help you calculate the lunch break, working, and payroll schedule on a daily, weekly, and monthly basis.
Time to Decimal Calculator from Calculator-Online. Enter the time in hours:minutes:seconds format and the tool will swiftly calculate its corresponding decimal notation. Mathematical Solution will be provided complete with Steps to calculate Hours, Steps to calculate Minutes, and Steps to calculate Seconds.
Calculator Online. Site provides a wide variety of calculators.

International Atomic Time (TAI) from Wikipedia, the free encyclopedia. "TAI" from the French name Temps Atomique International.

Mr. Dowling's Electronic Passport: Time and Space. Daylight Saving Time, Measuring Time, Years, plus A Look at the Stars, Aristotle's Conclusion, Copernicus, Galileo's Observations, Isaac Newton and Gravity, Longitude and Latitude, Seasons, Map Projections, and more.

Telling Time Without a Clock: Scandinavian Daymarks. Pointing at the Sun, Hours of Day, Hours of Night, Scandinavian Daymarks, Midday Daymark, Other Daymarks, Daymarks and Day Sections Among Other Peoples, How Daymarks Work, Class Projects: Schoolyard Daymarks and Classroom Noon-Line Project.

Time clock from Wikipedia, the free encyclopedia.

Time travel from Wikipedia, the free encyclopedia.

TIME TRAVEL - Is it Possible? YES! YouTube video, 2:46 min. A child explains Einstein's theory on the elasticity of time on The Science Channel's "10 Ways to See into the Future."

Predicting the Future - Email received July 2, 2016 entitled: We Live in Interesting Times. Original author: Udo Gollub at Messe Berlin. April 22, 2016. Berlin, Germany. Udo went to the Singularity University summit and reported the following key learnings on Facebook:

● 1998, Kodak had 170,000 employees and sold 85% of all photo paper worldwide. Within just a few years, their business model disappeared and they went bankrupt. What happened to Kodak will happen to a lot of industries in the next 10 years - and most people won't see it coming. Did you ever think in 1998 that 3 years later you would never take pictures on paper film again??? Yet digital cameras were invented in 1975. The problem was that the first ones only had 10,000 pixels and it took time to develop more definition in photos. So as with all exponential technologies, it was a disappointment for a long time, before it became way superior and became mainstream in only a few short years thereafter.

● The above will now start happening with artificial intelligence, health, autonomous and electric cars, education, 3D printing, agriculture, jobs and many other important parts of daily life.

Exponential Age. Welcome to the Exponential Age! Welcome to the 4th Industrial Revolution from Halo Media. "In 1998, Kodak had 170,000 employees and sold 85% of all photo paper worldwide. Within just a few years, their business model disappeared and they were bankrupt. What happened to Kodak will happen in a lot of industries in the next 10 years - and most people don't see it coming. Did you think in 1998 that 3 years later you would never take pictures on paper film again?

Yet digital cameras were invented in 1975. The first ones only had 10,000 pixels, but followed Moore's law. So as with all exponential technologies, it was a disappointment for a long time, before it became superior and mainstream in only a few short years. This will now happen with Artificial Intelligence, health, self-driving and electric cars, education, 3D printing, agriculture and jobs ..."

Software will disrupt most traditional industries in the next 5-10 years.
Uber is just a software tool. It doesn't own any cars, but is now the biggest taxi company in the world.
Airbnb is now the biggest hotel company in the world, although it doesn't own any properties.

Artificial intelligence:
Computers will become exponentially better in understanding the world.
This year [March 15, 2016], a computer beat the best Go player in the world, 10 years earlier than expected.
In the United States, young lawyers already don't get jobs because of IBM's Watson, where you can get legal advice (so far for more or less basic stuff) within seconds, with a 90% accuracy compared to 70% accuracy when done by humans.
So if you study law, stop immediately.
There will be 90% fewer lawyers in the future, only specialists will remain.
● See also: Watson (computer) from Wikipedia.
IBM Watson: Smartest Machine ever built - Documentary. YouTube video, 52:14 min.

Watson already helps nurses diagnose cancer, 4 times more accurately than human nurses.
Facebook now has a pattern recognition software that can recognize faces better than humans.
In 2030, computers will become more intelligent than humans.

Autonomous cars: In 2018, the first self driving cars will appear for the public.
Around 2020, the complete industry will start to be disrupted.

You won't want to own a car anymore, however, if you do want a car, then electric cars will start becoming mainstream by 2020.
Furthermore, cities will be less noisy because all cars will run on electricity.

You will call a car with your phone, it will show up at your location and drive you to your destination.
You will not need to park it, you only pay for the driven distance and can be productive while driving.
Our kids will never get a driver's licence and will never own a car.
It will change the cities, because we will need 90-95% fewer cars.
We can transform former parking space into parks.

Today, 1.2 million people die each year in car accidents worldwide.
With autonomous driving, we now have one accident every 100,000 km. That will drop to one accident in 10 million km and will save a million lives each year.
Most car companies might become bankrupt.
Traditional car companies still try the evolutionary approach and just build a better car, while tech companies (Tesla, Apple, Google) will take the revolutionary approach and build a computer on wheels. Udo spoke to a lot of engineers from Volkswagen and Audi; they are completely terrified of Tesla.

Insurance companies will have massive trouble. This is because without accidents, insurance will become 100x cheaper.
The car insurance business model will disappear.

Real Estate:
Real estate patterns will change - Because if you can work while you commute, people will move further away to live in a more beautiful neighborhood.

This facility will become incredibly cheap and clean.
Solar production has been on an exponential curve for 30 years, but you can only see the impact now.
Last year, more solar energy was installed worldwide than fossil.
The price for solar will drop so much that all coal companies will be out of business by 2025.

With cheap electricity comes cheap and abundant water.
Desalination now only needs 2kWh per cubic meter.
We don't have scarce water in most places, we only have scarce drinking water.
Imagine what will be possible if anyone can have as much clean water as he wants, for nearly no cost.

The Tricorder X Prize will be announced this year.
There will be companies who will build this type of medical device (called the "Tricorder" from Star Trek) that works with your phone taking your retina scan and will also be able to take your blood sample when you breathe into it. It then analyses 54 biomarkers that will identify nearly any disease. It will be cheap. So, in a few years, everyone on this planet will have access to world class medicine, nearly for free.

3D printing:
The price of the cheapest 3D printer came down from $18,000 to $400 within 10 years.
Within the same time period, it became 100 times faster.
All major shoe companies started 3D printing shoes.
Spare airplane parts are already 3D printed in remote airports.

The space station now has a printer that eliminates the need for the large amount of spare parts they used to have in the past.
At the end of this year, new smart phones will have 3D scanning possibilities. You can then 3D scan your feet and print your perfect shoe at home.

In China, the world's tallest 3D printed building - a five-story apartment block was built in 2015.
By 2027, 10% of everything that's being produced will be 3D printed.

Business opportunities:
If you think of a niche you want to go in, ask yourself: "In the future, do you think we will have that?" and if the answer is yes, how can you make that happen sooner?
If it doesn't work with your phone, forget the idea.
And any idea designed for success in the 20th century is doomed to failure in the 21st century.

70-80% of jobs will disappear in the next 20 years.
There will be a lot of new jobs, but it is not clear if there will be enough new jobs in such a short time.

Agriculture and food:
There will be a $100 agricultural robot in the future. Farmers in 3rd world countries can then become managers of their field instead of working all day in their fields.
Aeroponics will need much less water.

The first petri dish produced veal is now available and will be cheaper than cow produced veal in 2018.
Right now, 30% of all agricultural surfaces is used for cows. Imagine when we don't need that space anymore.
There are several startups who will bring insect protein to the market shortly. This will contain more protein than meat.
It will be labelled as "alternative protein source" (because most people still reject the idea of eating insects).

Human feelings:
There is already an app called "moodies" which can tell which mood you are in.
By 2020, there will be apps that can tell by your facial expressions if you are lying.
Imagine a political debate where it's being displayed when they are telling the truth and when they are not.

This currency will become mainstream this year and might even become the default reserve currency.
Bitcoin and cryptocurrencies - what digital money really means for our future by Alex Hern, The Guardian, 29 Jan. 2018.

Right now, an average life span increases by 3 months per year.
Four years ago, a life span used to be 79 years, now it's 80 years.
The increase itself is increasing, and by 2036, there will be more than one year increase per year.
So we all might live for a long, long time, probably way more than 100 years old.

The cheapest smart phones are already sold for $10 in Africa and Asia.
By 2020, 70% of all humans will own a smart phone and that means that most will have the same access to world class education.

TIME TRAVEL: What Einstein Did Not See. YouTube video, 4:29 min. Published on Aug 3, 2009 by timespacevector. "Watch time travel in three dimensions. From a book that presents a new approach to time and space. This new approach redefines time into two different components, a vector of Timespace and a scalar of Universal Time. Three-dimensional projections from four-dimensional Euclidean space can now visually illustrate time travel."

Time Travel. Everything you always wanted to know about time travel: Time and the Universe, How to build a time machine, A beginner's guide, Does time exist? Wormholes, Einstein Connection, Wormhole Engineering, The ultimate proof.

Time Travel from PBS - NOVA Online. Sagan on Time Travel, Traveling Through Time, Think Like Einstein (Hot Science), Timespeak.

Time Travel and Modern Physics from Stanford Encyclopedia of Philosophy. "Time travel has been a staple of science fiction. With the advent of general relativity it has been entertained by serious physicists."

Timekeeping at Sea National Maritime Museum, Royal Observatory Greenwich.

The Invention of Clocks. Part 1: Ancient Calendars - Aztec, Egyptian, and Sumerian Calendars - Stonehenge.
Part 2: Sun Clocks, Water Clocks, Obelisks
Part 3: Mechanical Pendulum Clocks and Quartz Clocks
Part 4: Atomic Clocks and Time Standards

Understanding Time. YouTube video, 52:50 min. "... the deep sense we have of time passing from present to past may be nothing more than an illusion ... Brian Greene takes us on the ultimate time-traveling adventure, hurtling 50 years into the future before stepping into a wormhole to travel back to the past ... he will reveal a new way of thinking about time in which moments past, present, and future ... exist all at once. This journey will bring us all the way back to the Big Bang, where physicists think the ultimate secrets of time may be hidden."

What's the Time? from Riverdeep Interactive sLimited. Units of Timekeeping, Pendulum Clocks, Quartz Crystal Clocks, Atomic Clocks.
What Is International Atomic Time (TAI)? From Time and Date. International Atomic Time (TAI) is one of the main components of Coordinated Universal Time (UTC), the time scale used to determine local times around the world. It tells us at which speed our clocks should tick.

What is time? - professor Renate Loll, Utrecht University. YouTube, 12:06 min. "Professor Renate Loll (Utrecht University) talks about the question 'What is time' from the perspective of theoretical physics. Often contra-intuitive but always fascinating, Loll reveals the secrets of a quantum theory of times."

www.timeanddate.com. A wide range of topics are covered: Time (World Clock, Search for City, Meeting Planner), Date (Calendar), Counters (countdown to any future date of your choice), Starting dates for Centuries and for Millennia, plus Latest updates.