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Time has long been a major subject of philosophy, art, poetry, and science. There are widely divergent views about its meaning; hence it is difficult to provide an uncontroversial definition of time. Scholars disagree on whether time itself can be measured or is itself part of the measuring system. Many fields use an operational definition in which the only definition attempted is that of the units used.
The measurement of time has also occupied scientists and technologists, and was a prime motivation in astronomy. Time is also a matter of significant social importance, having economic value ("time is money") as well as personal value, due to an awareness of the limited time in each day and in our lives. Units of time have been agreed upon to quantify the duration of events and the intervals between them. Regularly recurring events and objects with apparent periodic motion have long served as standards for units of time. Examples are the apparent motion of the sun across the sky, the phases of the moon, and the swing of a pendulum.
Time has historically been closely related with space, most obviously with spacetime in Einstein's General Relativity.
More on [ Time ]
A Walk Through Time - An illustrated history of timekeeping from ancient times to the present.
Meta Description: [ An illustrated history of timekeeping from ancient times to the present ]
Countdown - Calculate the exact time in days, hours, minutes and seconds from now until your birthday or any other event.
Daylight Saving Time - Why do we use daylight savings time and who invented it?
Meta Description: [ Seasons are caused by the tilt of the earth and the earth's rotation around the sun. Learn more about seasons in lesson designed for middle school students. ]
International Standard Date and Time Notation - International Standard ISO 8601 specifies numeric representations of date and time. It helps to avoid confusion caused by the many different national notations.
Meta Description: [ International Standard ISO 8601 specifies numeric representations of date and time. It helps to avoid confusion caused by the many different national notations. ]
Latitude and Longitude - Introduction to latitude and longitude, a way of calculating exactly where you are anyplace on earth and a way to tell time.
Meta Description: [ Introduction to latitude and longitude, on the globe and the celestial sphere; part of an educational web site on astronomy, mechanics, and space ]
Local Times Around the World - Find out what time it is anywhere in the world.
Meta Description: [ The World Clock shows current local time in cities and countries, in all time zones. ]
Make Your Own Star Clock - Learn how to tell time by finding constellations in the night sky.
Making a Horizontal Sundial - Learn how to make a sundial. Instructions are for beginners, intermediate, or advanced, and work for either the northern or southern hemispheres.
Making a Sun Clock - Before there were clocks, people used shadows to tell time. Learn how to make your own sun clock!
NPR : 'Seize the Daylight': A History of Clock Chaos - Benjamin Franklin first called for the government to tinker with clock hours in the 1780s. But it wasn't until World War I that the United States adopted daylight-saving time as a way to get more efficiency out of the day. Seize the Daylight Author David Prerau talks about the complicated politics and curious history of DST, and he shares an excerpt from his book. [4:54 streaming audio broadcast]
Meta Description: [ Benjamin Franklin first called for the government to tinker with clock hours in the 1780s. But it wasn't until World War I that the U.S. adopted daylight-saving time as a way to squeeze more out of the day. David Prerau explores the curious history of DST. ]
Time - Just how do we measure time and what has Greenwich England got to do with it?
Meta Description: [ Time changes as we move east or west, so most nations recognize twenty-four times zones. Learn more about time and time zones in lesson designed for middle school students. ]
Time Travel - Is time travel possible? See what Carl Sagan and Einstein had to say about time travel in this NOVA special.
Meta Description: [ NOVA Online presents Time Travel ]
What Time is it! - Gives the current time, synchronized by NIST. Close to 100 different time zones supported, as well as the ability to select the default time zone.
Meta Description: [ Your quest into the realms of AnalogX begins here... ]
When Does Daylight Savings Time Occur - Explaination of when and why we have daylight savings time.
Meta Description: [ Logan explains when and why does Daylight Savings Time occur. ]
World Time Converter - Provides online times converter and brief information about GMT/UTC.
Meta Description: [ Time and time zone converter. Readily tell the time anywhere in the world using our frequently updated time zone database. ]
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