Iran's daylight saving time is one day off. This is an English translation of what I just found (originally in Persian). The Gregorian dates in brackets are mine: -------------------------------------------------------------------------- Official Newspaper No. 13548-1370/6/25 [1991-09-16] No. 16760/T233 H 1370/6/10 [1991-09-01] The Rule About Change of the Official Time of the Country The Board of Ministers, in the meeting dated 1370/5/23 [1991-08-14], based on the suggestion number 2221/D dated 1370/4/22 [1991-07-13] of the Country's Organization for Official and Employment Affairs, and referring to the law for equating the working hours of workers and officers in the whole country dated 1359/4/23 [1980-07-14], and for synchronizing the official times of the country, agreed that: The official time of the country will should move forward one hour at the 24[:00] hours of the first day of Farvardin and should return to its previous state at the 24[:00] hours of the 30th day of Shahrivar. First Deputy to the President - Hassan Habibi --------------------------------------------------------------------------- This affects all the tz data starting from 1992.
From personal experience, that agrees with what has been followed for at least the last 5 years. Before that, for a few years, the date used was the first Thursday night of Farvardin and the last Thursday night of Shahrivar, but I can't give exact dates. I'm searching for evidence of the exact dates of each year in the newspaper archives.
But in the meanwhile, it'd be great to update the database with the attached patch. Iran will be in daylight saving in just a week, and current tz data is off one day. The new data is guaranteed to be correct from about 1998 until the end (2037). I have also changed the abbreivations to what is considered correct here in Iran, IRST for regular time and IRDT for daylight saving time. roozbeh