Hi, The timezone database currently lists Iran switching to standard time in 1946. I've been doing some research on the history of the adoption of standard time by Iran, and while it's very hard to find much, I found that the correct date is actually 1935. Here's an order from the Cabinet to the rest of the government to switch to Tehran time, which is mentioned to be already at +03:30: https://qavanin.ir/Law/TreeText/180138 Just in case that goes away, I also saved a copy at archive.org: https://web.archive.org/web/20220530111940/https://qavanin.ir/Law/TreeText/1... Here's my translation: "Circular on Matching the Hours of Governmental and Official Circles in Provinces Approved 1314/03/22 [=1935-06-13] According to the ruling of the Honorable Cabinet, it is ordered that from now on in all internal provinces of the country, governmental and official circles set their time to match Tehran time (three hours and half before Greenwich). It is required to mind the above order. For Minister of Judiciary, Dr Matin-Daftari" Now, I still haven't found out when Tehran itself switched to +03:30 (let's assume some time earlier in 1935), but it is clear that standard time in Iran started on 1935-06-13 and not 1946. Thanks, Roozbeh