Time zone

Key concepts

How Time zone connects to the ideas, people and events around it.

1. Greenwich Mean Time

   based on

   Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London. It was the world’s time standard before being superseded by UTC in 1972.

2. Coordinated Universal Time

   offset from

   Coordinated Universal Time (UTC) is the primary time standard by which the world regulates clocks and time. It combines atomic time with leap seconds to stay within 0.9 seconds of mean solar time.

3. Prime meridian

   defined by

   The Prime Meridian is the planet’s zero-degree longitude line that passes through Greenwich, England. It serves as the reference for longitudinal coordinates and time zones.

4. Daylight saving time

   adjusted by

   Daylight saving time (DST) advances clocks during warmer months to extend evening daylight. Many countries adjust their time zones seasonally to implement DST.

5. International Date Line

   bounded by

   The International Date Line roughly follows the 180° meridian in the Pacific Ocean. Crossing it results in a change of calendar date.

6. Tz database

   recorded in

   The tz database, also known as the IANA time zone database, provides historical and future time zone information for computer systems. It is widely used in operating systems and programming languages.

7. Sandford Fleming

   proposed by

   Sir Sandford Fleming was a Canadian engineer who advocated for worldwide standard time zones in the 1870s. His proposals led to the adoption of a global time zone system.

8. Standard time

   uses

   Standard time is the uniform time adopted by a region, replacing local solar time. It forms the basis for modern time zones.

Questions about Time zone