At the stroke of midnight, the first second of UTC, or Coordinated Universal Time, has already begun and is written something like (00:00). UTC can be thought of as a chemo-mechanical derivation used to gauge, in any Gregorian calendrical year, the proper position of the Earth as such situate in its rotation around the sun by resorting to measure Cesium transition under specific, controlled conditions.

Coordinated Universal Time models true solar time

Keep in mind that target time, in terms of objective, is referred to as UT1 (or "astronomical time"), referring in fact to the actual position of Earth on its yearly course around the sun relative to its correspondent, theoretical "sync" to the Gregorian calendar ofstandard 365-day time. UTC time is the derived estimate of UT1 time that by modern timing methods becomes re-calibrated from time to time to keep with UT1 time by an error factor of no more than 0.9 nanoseconds.

Leap seconds

UTC employs the device of positive and negative "leap seconds" to maintain a margin of error no greater than 0.9 seconds, as determined by International Earth Rotation and Reference System Service (IERS). Any correction is determined by the IERS well in advance and sends out a message to major time-keeping centers throughout the world six months prior to June and July, or December and January, when the new second is added. A positive leap second looks like (23:59:60) occurring prior to (00:00:00). And a negative leap second looks like (23:59:58) and (00:00:00) occurring successively. Whereas, an ordinary succession of seconds just before a new day begins looks like (23:59:58), (23:59:59), (00:00:00) in sequence on days when there are no leap seconds applied.

To-date, no negative leap seconds have been applied since the UTC standard replaced the former Greenwich Mean Time (GMT) standard in 1972 globally.

UTC time: Official clock

In practice, there is no actual, official UTC clock. Rather, to arrive at UTC time, a series of about ten clocks kept by the National Institute of Standards and Technology (NIST) are factored together into a "weighted average" from the more accurate clocks of the same collection to produce one single signal that contributes in fact to International Atomic Time (TAI) as well as to UTC time. The UTC estimate of NIST expresses as "UTC(NIST)." Similarly, the United States Naval Observatory (USNO) similarly keeps a number of atomic clocks used to express UTC time as "UTC(USNO)." These clocks remain calibrated regularly to keep a standard deviation error of no more than 20 nanoseconds. Together, either clock's time may be considered an official source of United States time.

UTC origin and rationale

Coordinated Universal Time was thought up originally by specialists of the International Telecommunication Union (ITU), whom proposed the idea in 1970. The gain involved cut out the various acronym references under GMT that had formerly been abbreviated based upon region name. "UTC" replaced territory-based abbreviations while retaining the same basic time zone logic of the GMT time scheme. The acronym itself further distances itself from territoriality by adopting a word arrangement that is not preferred by order of the acronym's correspondent words in any language.

Envisioning UTC

On any standard globe or map of the world can be found 360° degrees of longitude that fan out from 0° to 180° and back from -±180° to 0° across either hemisphere relative to longitudinal 0° of the Prime Meridian. UTC positions an absolute time zone every 7.5° degrees that spans an hour of time from 0 longitude of the Prime Meridian, along the same line of longitude as Zulu Time (UTC +0), and where Greenwich Mean Time originally applies, all the way to maximum longitudinal degreeof 180°. However, the UTC time zone varies its applicable geographic range between the North and South poles of earth, gerrymandering-style. UTC time is up to twelve hours ahead (UTC +12) and twelve hours behind (UTC -12) that base time of (UTC +0) and extends to the International Date Line, divided half-wise where the Bering Strait of East Russian Federation and West North American Alaska would technically be. Western Alaska (Seward Peninsula) situates to the East at (UTC-12), and the Russian Federation (Chukotka Peninsula) to the West at (UTC+12). More precisely, the International Date Line divides the islands of Big Diomede of the Russian Federation and Little Diomede of the Alaskan United States.

Understanding Coordinated Universal time is an exercise in comprehending longitude, cesium gauge instrumentation, and derived Earth:Sun annual rotational position relative to the Prime Meridian at 0° longitude. Twenty-four (24) longitudinal demarcations each at ±7.5° intervals apiece account for the hemispheric timing trend of each of the twelve hours ahead and twelve behind UTC +0 of the Prime Meridian. Cesium model timing devices estimate the proper mathematical time to account for a 365-day, 525,600-hour, 31,536,000 minute year to within 0.9 nanoseconds of accuracy, and recalibration is established through formal organizational procedures six months in advance. The final product is representative of annual Earth:Sun position correspondent to Gregorian calendrical time and taken from either UTC (NIST) or UTC (USNO) clock signal readings to establish official time in the United States.