Everything you need to know about how the world tells time.
A time zone is a region of the globe that observes a uniform standard time for legal, commercial, and social purposes. Time zones tend to follow the boundaries of countries and their subdivisions because it is convenient for areas in close commercial or other communication to keep the same time.
Most time zones on land are offset from Coordinated Universal Time (UTC) by a whole number of hours (UTC−12:00 to UTC+14:00), but a few zones are offset by 30 or 45 minutes.
Daylight Saving Time is the practice of advancing clocks during warmer months so that darkness falls later each day according to the clock. Regions that use DST adjust their clocks forward by one hour in spring and backward by one hour in autumn.
Not all countries observe DST. Near the equator, there is little variation in daylight throughout the year, so DST is generally not observed. Our live clocks automatically handle DST transitions for every city.
The International Date Line (IDL) is an imaginary line on the Earth's surface, generally following the 180° meridian, where the date changes as one travels east or west across it. Traveling eastward across the line subtracts one day, while traveling westward adds one day. This is why some UTC+14 regions are technically the first to experience a new day.