A time zone is an area that 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 frequent communication areas to keep the same time.
All-time zones are defined as offsets from Coordinated Universal Time (UTC), ranging from UTC−12:00 to UTC+14:00. The balances are usually a whole number of hours, but a few zones are offset by additional 30 or 45 minutes, such as India and Nepal.
Some higher latitude areas use daylight saving time for part of the year, typically by adding one hour to local time during spring and summer.