UTC – Internet and World Wide Web Time System: UTC has Replaced GMT as the Universal Time Standard

Many people around the world wonder when the “Message Detail” of their email shows the time in UTC, and not in GMT. Greenwich Mean Time (GMT) is widely considered as the international time system, but “UTC” is still largely unclear in the minds of many, and causes confusion.

In a casual sense, UTC and GMT are not different from each other. Therefore, a casual observer may assume “GMT” wherever “UTC” time is mentioned. But it may help to understand UTC more precisely because in technical terms, UTC has already replaced GMT as a standard time system. In fact, UTC replaced GMT as the basis of the primary reference time scale in most time zones way back in 1972. In the United States, UTC has been adopted as legal time in the Title 15 of the U.S. Code.

In technical terms, UTC is more advanced than GMT because it takes into account the gradual slowdown in the rotational speed of earth. UTC or “Coordinated Universal Time” is based on International Atomic Time. The technical difference between UTC and GMT may not be more than a small fraction of a second. Therefore, to a casual user it does not make a real difference. But in a technical context, where very high precision timings are required, UTC is the preferred alternative.

Internet and the World Wide Web

Most Internet and World Wide Web standards use the UTC time system. The Network Time Protocol that synchronizes the computer clocks over the Internet with that of the atomic clock makes use of UTC.

International Broadcasters

International Broadcasters, such as the BBC World Service, or even the amateur radio bands make use of UTC when they have to declare their broadcast timings and schedules.

Aviation

Aviation industry also clocks its timings in UTC. It is used for making weather forecasts, preparing flight plans, managing air traffic control clearances, and maps. UTC helps to eliminate confusion about time zones and Daylight Saving Time.

Military and Space Systems

Advanced military and space systems also use UTC for their time and date records. For defence equipment and communications equipment that requires very high degree of timings precision, UTC is the timing system of choice.

UTC makes use of high precision atomic clocks, shortwave time signals, and satellites to maintain its stringent levels of accuracy for a variety of scientific, navigational and communication purposes. That makes it the most advanced and dependable time system in the world today from a scientific perspective.