UTC, Z or GMT: what time is it, really?
For those of you that closely follow the Solar Impulse project, you might have wondered why we use the UTC and Z (pronounced “Zulu”) standard instead of regular GMT?
The main reason is that UTC (Coordinated Universal Time), or Z for pilots and the military, although the same as GMT (Greenwich Mean Time) it’s the standard used in aviation. In fact, to avoid issues related to daylight savings time, flight plans, air traffic control and weather forecasts, the aviation world has chosen follow UTC, or world time also called Zulu in technical flight communications, to ensure everybody’s on the same page. Can you imagine if you were sitting in a commercial airplane and the pilot began arguing with the air traffic controller about the scheduled landing time? You would probably, for the first time, wish you were in an exit seat not to mention what the skies would look like: worse than chaotic central Rome!
What is interesting about UTC is that it’s based on International Atomic Time whose ticking is kept by atomic clocks scattered in 70 national laboratories across the globe. However, because of the slow decrease in the Earth’s rotational time, UTC needs to be regularly updated. UTC is worse than the Swiss: it’s regularly running ahead of time, approximately one second every 800 days. The result is that the 21th Century will require a leap second every 250 days and two leap seconds in the 22nd Century. But don’t get overly enthusiastic. This doesn’t mean that our days are becoming significantly longer. Unfortunately we’ll only gain one second in 50,000 years!
And finally, why the acronym “UTC” if it’s supposed to mean Coordinated Universal Time? Once again, the ancient rivalry between Descartes and Shakespeare resurfaces. When, in 1961, the International Telecommunications Union and the International Astronomical Union convened to find standard terminologies in all languages, English-speakers proposed CUT while French-speakers lobbied for TUC (temps universel coordonné). Making great proof of tact and diplomacy, the two International Unions knew better not to spark dormant resentments on the other side of the Channel and swiftly found an adequate compromise, known today as UTC.
For those of you that closely follow the Solar Impulse project, you might have wondered why we use the UTC and Z (pronounced ...