As the Earth spins on its axis, various regions receive light or darkness. In the late 1880s, a team of scientists introduced a method of subdividing the world into various time zones. The scientists studied Earth's movements after which they came up with 24 time zones which are theoretically drawn on the world map. If every time zone were one hour apart, there would be a total of 24 across the world. However, some of them have 30 and 45 minutes offsets, a situation which makes the total number in the world much higher.
Time Zone Borders Differ
The scientists who introduced the time zones created them as being 15 degrees wide to denote a one-hour variance in mean solar time. The actual borders drawn on a time zone map, however, adheres to internal and external borders and they hardly correspond precisely with the 15-degree borders on a time zone map. India for example, despite being an extensive territory, observes one national time as does China. Although India's cities previously were in different time zones, the single national time was allegedly introduced in the colonial era to coordinate work on the railway network.
Daylight Saving Time Zones
The time zone name and time change during Daylight Saving Time (DST). The terms "summer" or "daylight" are subsequently included in the name while the local time is typically set forward one hour. This practice is meant to increase the span of the evening daylight while giving up usual sunrise times. The concept of daylight saving was the idea of George Hudson, a New Zealand astronomer. However, different countries do not adhere to DST including Peru, Indonesia, and Western Australia, most of Africa, Japan, Australia's Northern Territory, and Argentina.
Defined By UTC Offset
Each region on Earth has its distance measured east or west of the prime meridian which is theoretically placed in Greenwich, London in the UK. The meridian also serves as the reference mark for Coordinated Universal Time with one hour for every 15 degrees longitude. A particular longitude in degrees has to be divided by 15 to determine the precise time zone in hours.
Countries With The Most Time Zones
France observes twelve time zones, mainly because it has many overseas territories. The official time for Metropolitan France is set as GMT+1 while the time zones in its international territories fall between UTC-10:00 in most regions of French Polynesia to UTC+12:00 in the territories of Wallis and Futuna. The US law identifies nine standard time zones which include its territories, and there are an additional two time zones that are unofficial. Most parts of the US also adhere to Daylight Saving Time in many of the summer, fall, and spring months. The time zones of the US include Hawaii, Mountain, Atlantic, Samoa, Alaska, and Pacific. Russia observes 11 time zones including Omsk, Moscow, Yakutsk, Magadan, Samara, Vladivostok, Yekaterinburg, and Kamchatka. The time zones were defined in 1992 when the nation's territories were being established in the aftermath of the Soviet Union's dissolution.