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What is UTC?

Basically, it is an acronym for Coordinated Universal Time. Why they don't use CUT is explained somewhere but it has to do with they wanted it to be a universal name. So they didn't choose an acronym. UTC does not stand for anything, it is just a play on letters. But the way they calculate UTC is important. They use many atomic clocks from all over the world. It is not just one clock, it is around 250 of them.

Then UTC is used by other organizations to synchronize their clocks. For example, UTC(NIST) is the NIST's time, based off the UTC. The NIST_Time_and_Frequency_Division_homepage is a great place to start learning about time measurement technology and its history and current state of the art, including the NIST-F1 Cesium Fountain Atomic Clock.

Most of us know that to convert UTC to our local time, we must add or subtract a certain number of hours. For my location in the Eastern United States, in the Eastern Time Zone, I subtract 4 hours. How did I know that? Easy, just go to the What_Time_Is_It? page and it said the current time was 20:43:35 UTC. Well, I looked at my system time which of course is in local time and it said 16:43 so there is a 4 hour time difference. Easy enough? Also, daylight savings time is in effect right now. In either October or November, our clocks will roll back an hour and thus there will be a 5 hour time difference, since UTC always stays the same and has no daylight savings time plan.

Next:
So are we done?

Setting the clock in Linux part 3
The NTP program
Running ntpdate
What is UTC?
So are we done?
Conclusions
Resources

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