Time zone
From Halbeeg, the open encyclopedia · Af-Soomaali
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A time zone is a region of the Earth in which people use a standard uniform time. Rather than each city using its own local solar time (apparent solar time based on the sun's position), countries choose a single standard time spanning a large area, to facilitate transportation, communication, and commerce.
Time zones are defined by their difference from Coordinated Universal Time (UTC), the global standard. For example, UTC+3 means three hours ahead of UTC. Most differences are whole hours, but some are half-hours or quarter-hours, such as UTC+5:30 and UTC+5:45.
Origins of the concept
Before the late nineteenth century, each city kept time based on the sun's position in the sky. When railways and telegraphs connected distant places, this variation created scheduling confusion and complications. To solve this, a system of time zones was proposed based on lines of longitude, dividing the Earth into approximately 24 sections, each covering about 15 degrees.
Boundaries and political decisions
Time zone boundaries do not always follow longitude lines. Countries adjust them to suit national borders, administrative regions, and economic ties. Some countries, such as China, use a single time zone across a vast area; others, like Russia and the United States, have multiple time zones. Changes to time zones are political decisions made by governments, sometimes subject to revision.
Daylight saving time
Many countries far from the equator use daylight saving time, moving clocks forward by one hour and then returning them. The purpose is to make better use of daylight during the hours when people are active. Countries near the equator, where day and night lengths are similar year-round, generally do not use it.
Technology use
Computer systems store UTC internally and then convert it to the user's time zone. Time zone data is maintained in a database that updates whenever a government makes changes, so programs can recognize new dates. Aircraft, financial markets, and communication networks depend on keeping this information accurate.