aikavyöhyket

Aikavyöhyket, also known as time zones, are regions of the Earth that observe a uniform standard time for legal, commercial, and social purposes. They are based on the fact that the Earth rotates, causing the sun to appear at different positions in the sky at different longitudes. A full rotation takes 24 hours, so ideally, the Earth would be divided into 24 time zones, each spanning 15 degrees of longitude.

However, political and geographical boundaries often lead to deviations from this ideal. Countries and regions may adopt time zones that do not strictly follow longitude lines to maintain administrative consistency or for practical reasons. For instance, a country might span multiple ideal time zones but choose to observe a single time zone for simplicity. Conversely, a large country might be divided into several time zones, even if the longitude difference is not exactly 15 degrees per zone.

The system of time zones was standardized internationally during the late 19th century. Greenwich Mean Time (GMT), now largely superseded by Coordinated Universal Time (UTC), was established as the reference point. Most time zones are defined as offsets from UTC, such as UTC+1, UTC-5, etc. Daylight Saving Time (DST) is another phenomenon related to time zones, where clocks are advanced by an hour during warmer months to make better use of daylight. This practice is observed in many but not all regions that use time zones. The implementation and rules of DST can vary significantly by country and even by region within a country.