Time zone

A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time.

Time zones are defined as 1 or 2 offsets from Coordinated Universal Time (UTC), and (if 2 offsets are used) the days when the offset changes. Some time zones switch between offsets throughout the year due to daylight saving time (DST).[1] The UTC offsets range from UTC−12:00 to UTC+14:00, and are usually a whole number of hours, but a few zones are offset by an additional 30 or 45 minutes (such as in India, South Australia and Nepal).

Areas of extreme latitude are more likely to use DST. DST is usually used for about half of the year, typically by adding one hour to local time during spring and summer.