Summer Time and Time Zones

Daylight Saving Time (DST) in the time zone structure

DST designations and abbreviations

Wherever it is used, Daylight Saving Time (DST) adds another time zone, defined as an area (country or region) where the same time is observed.

Daylight Saving — the practice of advancing the clocks by one hour — extends beyond the astronomical summer, which starts with the Summer Solstice and ends with the Autumn (Fall) Equinox.

In countries that observe DST, clocks go forward by one hour at various dates in March or April, and go back to Standard Time at the end of October or November.

With DST in use, the original time zone structure became much more complicated. Countries or regions that observe DST change their effective time zone twice a year.

Time zone designations are both civilian and military. The list of civilian time zones includes Daylight Saving variants. Military time zones do not use DST.

Just like standard time zones, Daylight Saving Time (DST) zones are indexed by the zone hour value: the offset or time difference relative to GMT or its successor, UTC (Coordinated Universal Time).

Summer Time (or Daylight Saving) Time Zones in use

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