The Indian Standard Time (IST) :
- The Indian Standard Time is calculated from 82°30’E meridian passing through Mirzapur.
- IST is plus 5.30 hours from the GMT.
- It does not take into account daylight saving time along with other seasonal factors. India has only one timezone.
Greenwich Mean Time (GMT) :
- Greenwich Mean Time (GMT), the name for the mean solar time of the longitude (0°) of the Royal Greenwich Observatory in England.
- The meridian at this longitude is called the prime meridian or Greenwich meridian.
Important Points
International dateline :
- The prime meridian also helps establish the International Date Line.
- The Earth's longitude measures 360o, so the halfway point from the prime meridian is the 180 longitude line.
- The meridian at 180 longitudes is commonly known as the International Date Line.
- As you pass the International Date Line, you either add a day (going west) or subtract a day (going east.)

