It would be very confusing if the clock said midday in one place and the sun was high in the sky, but in another place at midday the sky was pitch-black and full of stars. Thank goodness someone had the bright idea of time zones.
Universal Time. Depending where you are on the planet, it might be the middle of the day or the middle of the night, because the Earth is orbiting the Sun. Of course, before time zones clocks weren’t set at the same time for everyone and no one ate their lunch at 3 a.m. or had breakfast at bedtime.
People used the Sun as their guide and the time was set locally, when the Sun was overhead, it was midday. As new ways to travel and communicate were invented, knowing the exact time in different parts of the world became more and more important, and a standard time was needed.
Sir Sandford Fleming first proposed time zones for the whole world in 1876. In 1884 an international conference at the Royal Observatory in Greenwich, London, adopted the time zones we know today. Planet Earth rotates on its axis 15 degrees every hour, so the world is divided into 24 15-degree sections, with the clocks in each section set an hour apart (at least, that’s how it works for most of the world).
The zones are all measured from Greenwich, which the 1884 conference decided was the Prime Meridian. The time at Greenwich is known as Greenwich Mean Time or, more grandly, Universal Time.
The Pacific country of Kiribati used to have two different time zones. The eastern half of the country was a whole day and two hours behind the western half! In 1995 the time zone was changed so that Kiribati clocks all told the same time.