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Articles About Timekeeping (33)

UTC – Coordinated Universal Time

Coordinated Universal Time (UTC) is the basis for civil time today. This 24-hour time standard is kept using highly precise atomic clocks combined with the Earth's rotation. more

International Date Line (IDL)

The International Date Line (IDL) is an imaginary line of longitude on the Earth’s surface located at about 180 degrees east (or west) of the Greenwich Meridian. more

UTC & GMT – Same Difference?

Greenwich Mean Time (GMT) is often interchanged or confused with Coordinated Universal Time (UTC). But GMT is a time zone and UTC is a time standard. more

How Do Atomic Clocks Work?

Atomic clocks are among the most accurate timekeepers in human history. Just how precise are they and how do they work? more

International Atomic Time

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. more

How Leap Seconds Work

Leap seconds have been added to clocks worldwide since 1972. Why are they needed and why the Earth is slowing down? more

What are Leap Seconds?

Every now and then a leap second is added to Coordinated Universal Time (UTC) in order to synchronize clocks worldwide with the Earth's ever slowing rotation. more

What is Local Mean Time (LMT)?

Use a sundial to determine the time of day and you will probably be off by a few minutes. That's where LMT comes into play. How is it measured and what is it used for? more

Alternative Time Systems

Astronomers use other measures of time, such as Terrestrial Time (TT), which is 32.184 seconds ahead of International Atomic Time (TAI). more

What Is a Time Zone?

A 'Time Zone' refers to any region where the same standard time is kept. Interactive Time Zone Map for current Time Zones worldwide. more

Why Do We Have Time Zones?

Which country first adopted time zones? Where and why were standard time zones first adopted and why were time zones created? more

GMT or BST in the UK?

The UK is not on Greenwich Mean Time (GMT) all year. During Daylight Saving Time the correct time zone is British Summer Time (BST). more

Why UTC – not CUT?

The abbreviation for Coordinated Universal Time is UTC. Why is it not abbreviated as “CUT” or “TUC”? more

The Revised Julian Calendar

The Revised Julian calendar is one of the most accurate calendar systems ever developed. How does it work, and why don't we use it? more

The Daylight Saving Time Debate

DST has become a political issue, while others debate whether setting the clocks one hour ahead in the spring has the intended effect of conserving energy or reducing road accidents. more

Daylight Savings or Saving?

“Daylight saving time” is the correct term, but “Daylight savings time” with an “s” is at least as commonly used. more

History of DST

Daylight Saving Time (DST) is used to save energy and make better use of daylight. Today, daylight saving time (DST) is used in many countries. more

Daylight Saving Time – DST

Daylight Saving Time aka Daylight Savings Time, DST or Summer Time. Clocks go forward 1 hour in the spring and back in the fall to make better use of natural daylight. more

One Hour Ahead or Back?

Which way do the clocks go? "Spring forward or fall back" is just one way to remember which way set the clocks for Daylight Saving Time (DST). more

Summer Time or DST?

Summer time is often used to describe Daylight Saving Time (DST), especially the United Kingdom. Winter time instead of standard time is also a common variation. more

Transition to DST

Daylight Saving Time or summer time transition, what time does DST start or finish? more

Equation of Time

Why doesn't the year's earliest sunset occur on the Winter Solstice, even though it is the shortest day of the year in terms of daylight? more

Timekeeping by Stars

Out and about at night without a watch or a smartphone readily available? If you are in the Northern Hemisphere use the Big Dipper and the North Star to tell the time. more

A Year Is Never 365 Days

The definition of a tropical year is the time it takes the Earth to complete a full orbit around the Sun. It is approximately 365.242189 days long. more

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