Universal Time (UTC)
Quillcards and Coordinated Universal Time
Quillcards members send ecards to people in countries all over the world. This has an implication for when their ecards are sent and when they arrive because the ‘current’ time is not the same throughout the world. It is set according to time zones.
The Quillcards default time zone is United States Eastern time, which Quillcards members can change to whichever time zone they wish.
You can check times throughout the world here at Time And Date. (Note that it opens in a new browser window.)
What is Coordinated Universal Time?
One of the less understood time zones is Coordinated Universal Time (UTC). It is not time measured in any particular place, but rather it is time measured by caesium atomic clocks and it was adopted as an international standard in 1967.
Of course, caesium clocks had to be set by reference to time somewhere, and Greenwich Mean Time (sometimes called ‘London Time’) was chosen.
For all practical purposes, UTC is the same as Greenwich Mean Time But they are not exactly the same and a leap-second was added to UTC at the end of 2008 to coordinate it with Greenwich Mean Time.
What is Greenwich Mean Time?
Greenwich Mean Time was adopted as the time standard around the world at the Washington Meridian Conference of 1884. it is the time calculated by the Greenwich Observatory in London by reference to the Earth’s rotation and the position of the sun in the heavens.
The signatories to the Washington Conference were happy to adopt Greenwich as the meridian line because the continuation of the meridian line on the other side of the world lies mostly over water, which is convenient for the date line.
Why was UTC Developed?
UTC was developed as a means of measuring time independent of the Earth’s rotation. And the need for this was because the Earth is slowing down in its rotation.
The first successful caesium atomic clock – which measures the vibrations of caesium atoms – was built in Teddington, England in 1955.
Once the reliability of these clocks was proven and established, the time measured by them was adopted internationally, and now there are many such clocks in various parts of the world. Today there are approximately 70 caesium clocks in the United States alone.
But UTC has to coordinate with Greenwich Mean Time because if we followed time according to UTC and ignored Greenwich Mean Time, then eventually we would find ourselves out of synchronization with what we see out of the window.
Out of Synchronization
Since the first observation of the vibration of caesium in 1958, the Earth has only moved 33 seconds out of synchronization, so the discrepancy is small. Nontheless to correct the discrepency, leap-seconds are introduced every few years, and 2008 was one such year.
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