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Articles about Timekeeping (28)

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

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

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

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

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

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

Transition to DST

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

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 atomic clocks 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 atomic clocks with the Earth's ever slowing rotation. more

Why UTC – not CUT?

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

Is There a Perfect Calendar?

Our calendar does not accurately reflect the length of a tropical year, the time it takes Earth to complete a full orbit around the Sun. Why is that so and are there other calendars that do a better job? 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 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

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

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

A Year Is Never 365 Days

The definition of a tropical year, also known as a solar year, astronomical year, or equinoctial year, is the time it takes the Earth to complete a full orbit around the Sun, and it is approximately 365.242189 days long. 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

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