Iran Standard Time

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Iran Standard Time (IRST) or Iran Time (IT) is the time zone used in Iran. Iran uses a UTC offset UTC+03:30. IRST is defined by the 52.5 degrees east meridian, the same meridian which defines the Iranian calendar and is the official meridian of Iran.

Between 2005 and 2008, by decree of President Mahmoud Ahmadinejad, Iran did not observe daylight saving time (called Iran Daylight Time or IRDT).[1][2] It was reintroduced from 21 March 2008.

Daylight Saving Transitions Dates[edit]

Iran is unusual in that the dates of DST transitions aren't based on a rule such as the third Monday in September. So in most countries, DST transitions occur on the same weekday every year, but not in Iran.[3]

The Iranian DST starts on March 22 and ends on September 22 each year with the exception of leapyears in which the DST starts and ends one day prior.

Sat, Mar 22, 12:00 AM
Mon, Sep 22, 12:00 AM
Sun, Mar 22, 12:00 AM
Tue, Sep 22, 12:00 AM
Mon, Mar 21, 12:00 AM
Wed, Sep 21, 12:00 AM
Wed, Mar 22, 12:00 AM
Fri, Sep 22, 12:00 AM
Thu, Mar 22, 12:00 AM
Sat, Sep 22, 12:00 AM

Time zone changes[edit]

Period in use Time offset from GMT Name of Time
1800 – 1946 UTC+03:25:44 Iran Standard Time (IRST)
1947 – 1977 UTC+03:30 Iran Standard Time (IRST)
1977 – 1979 UTC+04:00
Iran Standard Time (IRST)
Iran Daylight Time (IRDT)
1979 – 1980 UTC+03:30
Iran Standard Time (IRST)
Iran Daylight Time (IRDT)
1981 – 1990 UTC+03:30 Iran Standard Time (IRST)
1991 – 2005 UTC+03:30
Iran Standard Time (IRST)
Iran Daylight Time (IRDT)
2006 – 2007 UTC+03:30 Iran Standard Time (IRST)
2008 – present UTC+03:30
Iran Standard Time (IRST)
Iran Daylight Time (IRDT)

IANA time zone database[edit]

The IANA time zone database contains one zone for Iran in the file, named Asia/Tehran.

See also[edit]


  1. ^ "Iran will not observe DST". 20 March 2007. Retrieved 9 May 2010. 
  2. ^ "Time zone and daylight saving time for Iran – Tehran between 2010 and 2019". Retrieved 9 May 2010. 
  3. ^ "Time Changes in Tehran over the years".