UTC: Coordinated Universal Time

Universal Coordinated Time (UTC) is the standard 24-hour measurement of time used worldwide. This measurement of time is used to centrally regulate and set our clocks to.

Greenwich Mean Time (GMT) was officially replaced with Universal Coordinated Time (UTC) in 1972 as the universal standard of time.

Astronomers over the past hundreds of years have perfected the way to tell time!

An example of UTC as you would see it on time.is/UTC

The History Behind UTC

In 1884, the International Meridian Conference held in Washington DC decided that the Prime Meridian in Greenwich, England would serve as the point of which all time zones in world would be measured from. Greenwich Mean Time (GMT) was adopted thereafter and recognized around the world.

Through a timeline, we can see how history changed the way time is measured and was coordinated worldwide.

December 31, 1925

  • Astronomers continued to research time measuring it daily, noon to noon.
  • Astronomers introduced a 12-hour break in the continuity of time causing a loss of 12 hours. This new time was called Greenwich Mean Astronomical Time (GMAT.) GMAT was the standard by which astronomers measured time.


  • The International Astronomical Union (astronomers) replaced GMT with what was referred to as “universal time” although it was not yet recognized as UTC
  • “Universal time” replaced the astronomoer’s GMAT.
  • This changed did not apply to the general population as it was adopted for astronomical research only.


  • The International Astronomical Union (astronomers) recognized that there were three versions of their “universal time.”

UT0 – measured the Earth’s rotational axis in respect to a site that was observing it.

UT1 – did the same thing UT0 did but also measured the position of the pole in respect to the site that was observing it making small corrections to be able to produce a time scale.

UT2 – did the same thing UT1 did but used a seasonal variant to account for the Earth’s rotational speed seasonal difference.


  • The Royal Observatory (Greenwich,) National Physical Laboratory England, and the U.S. Naval Observatory all agreed to coordinate time/frequency transmissions based on UT2.

January 1, 1960

  • The International Time Bureau coordinated an  international/universal coordination of time/frequency which became known as UTC.


  • UTC was internationally implemented replacing GMT.

Time Blows The Mind…

If we knew the calculations, astronomical observations, worldwide coordination, and the international time associated groups that keep our clocks running on time, it would be more than the average person could handle!

If you ever have some free reading time, check up on the standards of measurement on a global basis. The reading material alone is in of itself is bulkage that extends the typical mind.

Next time you check your watch or glance at the clock, think about how every second has been accounted for in our world.


(n.d.) Coordinated Universal Time (UTC), CCTF 09-32, International Bureau of Weights and Measures, France, Retrieved from: https://www.bipm.org/cc/CCTF/Allowed/18/CCTF_09-32_noteUTC.pdf