World times/time zones: Everyone knows the time. But how relative time becomes clear when traveling long distances. If you fly from Berlin to London, the time is one hour earlier than on your watch. If you fly from Munich to Moscow, it will be two hours later. The simple reason is that the cities and countries have different time zones. Many tourists and business travellers consider the associated time difference. But what is the reason for the other times?
The astronomical explanation: midday is when the sun is at its highest point
Up until the 19th century, many places still had their own time. These places were organized according to an astronomical phenomenon. This is because the sun is at its highest at “midday.”
However, if all places on Earth had the same time, the sun would not reach its zenith at midday in most places. On the contrary, it would even be pitch dark in many places. Therefore, noon for some would be a night for others. This is why the times differ.
How are times of day created?
Illustrated: The sun shines “from the side” on half the globe. On this half, it is day. On the other hand, it is night. As the earth rotates around itself from west to east, it practically rotates into the daylight. This is why the sun rises in the east. At midday, i.e., when a place is exactly in the middle of the half of the day illuminated by the sun, the sun is at its highest due to the earth’s curvature.
It is, therefore, not to be expected that people on the other half of the earth would also want to refer to this position of the sun as midday. For this reason, people had their own local times for a long time. At the latest, this was associated with time chaos during the boom of the railway’s time zone concept. Travelers had to adjust their watches in practically every town, and the timetables were different at every stop.
GMT – Greenwich puts an end to the chaos
The United States ended this development in 1884 with the introduction of GMT. This abbreviation stands for Greenwich Mean Time. GMT stands for 12 o’clock in Greenwich. This is an averaged definition of the hours according to the sun’s position, considering and adjusting for the seasons, the effects of the tilt of the earth’s axis, etc.
The decisive point, however, was that those responsible divided the earth into 24 time zones, which were roughly oriented to the meridians and had a distance of 15 degrees. 360 degrees of longitude divided by 24 hours of the day results in this 15-degree deviation when evenly distributed. These time zones are essentially still in use today.
Note: Not all time zones are 15 degrees wide. The aim was to keep the same time in all countries. This is why time zone boundaries deviate from the longitude system. This was impossible only in large countries such as Russia, Canada, the USA, etc., so there are more time zones. On the other hand, Central Europe uses Central European Time, which is a much wider time zone than just the typical 15 degrees of longitude. The idea of a “uniformly split orange” as an image for the time zones on Earth is, therefore, misleading.
Time zones, world map: Each zone, defined in this way, had its own time and was binding for all places. Starting from the time zone in which Greenwich is located (GMT 0), each time zone to the east was one hour further ahead than the one before it (Berlin, for example, GMT +1), and each time zone further west was one hour behind the one to the east (GMT -1). This created a standardized time difference.
Good to know: The calculation based on Greenwich also means that the International Date Line lies in the Pacific, between the 12th and 13th time zones. This is because some are +12 hours ahead, while others are -12 hours behind.
This meant that, on the one hand, there were binding times within the time zones, and, on the other, it was clear at which points travelers reached a new time zone. As these time zones were very broad, there was less need to adjust the time, which made life easier and boosted the economy.
Today, Greenwich Mean Time has been replaced by UTC. To be understood as coordinated universal time, this time corresponds in principle to GMT. Based on UTC, local times are given as UTC +2 or UTC -4, for example. This refers to world time information that can be calculated more quickly. This is because the time is still different in all time zones.
- hp/picture: Bild von Gerd Altmann auf Pixabay
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