Summer Time and Time Zones

Daylight Saving Time (DST) extends beyond the astronomical summer

Civilian designations relative to GMT

There are 25 integer World Time Zones from -12 through 0 (GMT) to +12. Each one is 15° of Longitude as measured East and West from the Prime Meridian of the World at Greenwich, England.

There are both civilian designations which are typically three letter abbreviations (e.g. EST) for most time zones. In addition there are military designations. These use each letter of the alphabet (except 'i') and are known by their phonetic equivalent. E.G. Greenwich Mean Time (civilian) or z = Zulu (military and aviation).

• For details of Daylight saving (Summer) Time see here

Summer Time (or Daylight-Saving) Time Zones

There are many Daylight saving Time (DST) time zones, indexed by the zone hour value relative to both Greenwich Mean Time (GMT) and British Summer Time (BST).

See : Standard (or Winter Time) Zones