Iran Daylight Time

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). It was reintroduced from 21 March 2008.

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.

2014
Sat, Mar 22, 12:00 AM
Mon, Sep 22, 12:00 AM
2015
Sun, Mar 22, 12:00 AM
Tue, Sep 22, 12:00 AM
2016
Mon, Mar 21, 12:00 AM
Wed, Sep 21, 12:00 AM
2017
Wed, Mar 22, 12:00 AM
Fri, Sep 22, 12:00 AM
2018
Thu, Mar 22, 12:00 AM
Sat, Sep 22, 12:00 AM

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

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Wikipedia