This project documents the use of the Lunar Hijri/Islamic (AH) calendar in Iran over the years. It is intended for historically accurate date conversion, as well as comparing astronomical predictions with what actually happened on the ground.

The starting day of each AH month we have found in any reliable source is listed with the Gregorian equivalent. Since not all sources agree, best efforts have been made to resolve conflicts and provide the most reliable resolution.

Dates where the observation on the ground is known to have differed with the published calendar of the time are marked with an asterisk. The listed Gregorian date for such months is the date the beginning of the month was observed, not the precalculated day.

The work is not considered final and the data is expected to become more accurate as more research is done.