UTC (Zulu time) is used by pilots, astronauts, weather, an international space station for good reason
It is easy to realise that pilots flying across time zones, the space station high above the Earth, an orbiting satellite, a ham radio operator scheduling a broadcast that is received in multiple countries, etc cannot rely on time zones and daylight savings times to be calculated in real-time by various people using at different points across Earth timezones (or even in space). Accuracy and precise pinpointing of time is needed (let's not go into the metric vs imperial measurement systems…).
So GMT (Greenwich Mean Time) is familiar to many people and is quite an old term in use. It turns out the original Greenwich time was actually calculated around midday and not from 00:00 midnight. Different versions of GMT existed based on 12 hours prior to midnight and another for post-midnight. In 1928, the term Universal Time (UT) was introduced by the International Astronomical Union to refer to GMT, with the day starting at midnight. In 1961, the Bureau International de l'Heure began coordinating the UTC process internationally (but the name Coordinated Universal Time was not formally adopted by the International Astronomical Union until 1967). UTC does not change with a change of seasons, but local time or civil time may change if a time zone jurisdiction observes daylight saving time (summer time).
The timezone using UTC is sometimes denoted UTC±00:00 or by the letter Z—a reference to the equivalent nautical time zone (GMT), which has been denoted by a Z since about 1950. Time zones were identified by successive letters of the alphabet and the Greenwich time zone was marked by a Z as it was the point of origin. The letter also refers to the "zone description" of zero hours, which has been used since 1920 (see time zone history). Since the NATO phonetic alphabet word for Z is "Zulu", UTC is sometimes known as "Zulu time". This is especially true in aviation, where "Zulu" is the universal standard. This ensures that all pilots, regardless of location, are using the same 24-hour clock, thus avoiding confusion when flying between time zones. On electronic devices that only allow the current time zone to be configured using maps or city names, UTC can be selected indirectly by selecting Reykjavík, Iceland, which is always on UTC and does not use daylight saving time.
There is a lot more technical detail about how adjustments have been handled with leap seconds etc and the future of UTC which can be read at https://en.wikipedia.org/wiki/Coordinated_Universal_Time.
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Coordinated Universal Time – Wikipedia |