tímabelti

A tímabelti, or time zone, is a region of the Earth that observes a uniform standard time for legal, commercial, and social purposes. Time zones are determined by their angular displacement east or west of the prime meridian, which is the meridian of longitude passing through Greenwich, London, England. Theoretically, the Earth is divided into 24 time zones, each spanning 15 degrees of longitude, to account for its rotation of 360 degrees in 24 hours.

However, actual time zone boundaries are not strictly determined by longitude. They often follow political or geographical boundaries, such as national borders, state lines, or rivers, to simplify administration and communication. This can result in irregular time zone shapes. Some countries or regions may also observe daylight saving time, where clocks are advanced by an hour during warmer months to make better use of daylight.

The system of time zones was first proposed by Canadian railway planner Sir Sandford Fleming in the late 19th century and was widely adopted internationally in the early 20th century. This standardization greatly facilitated international travel and communication. UTC (Coordinated Universal Time) serves as the primary time standard by which the world regulates clocks and time. Time zones are expressed as offsets from UTC, for example, UTC+1 or UTC-5.