The actual birth date of Dr. Mossadegh is the subject of some speculation. The most common date cited in published materials is May 20, 1882 - the date that Dr. Mossadegh himself believed to be true. The date May 19, 1882 also appears in different writings. Yet our conclusion is that Mossadegh was actually born nearly a month later.

In the handwritten note shown above, Mossadegh writes the Islamic Lunar Calendar date of 29 Rajab 1299 or May 20, 1882 and the Iranian Solar Calendar date of 29 Ordibehesht 1261 as his birth date. These numbers, however, do not correspond when one uses the available computer generated calendar converters! In this case, the date for the Iranian and Gregorian calendars match but not the date for the Islamic calendar.

In his book Mohammad Mossadegh: A Political Biography, Farhad Diba arrives at a more divergent date and states that Mossadegh was born on 26 Khordad 1261 (June 16, 1882). Diba attributes the source of the discrepancy to the following: 

"When he [Mossadegh] decided to leave for Europe, he was obliged to register his date of birth and obtain an identity card as a prerequisite for a passport. The usual tradition was for parents to write the date of birth of their children on the inside cover of the family Koran. Since this Koran was not on hand, Mossadegh registered with section (Precinct) 3 of Tehran police, and there was confusion in converting the Arabic (Ghamari) year into the Iranian (Shamsi) calendar effectively making him older than he really was... In any case, the family Koran was eventually found in the last decade of his life, proving his age beyond doubt."  

Unfortunately Diba does not provide any evidence, such as a copy of the page in Koran, to support this claim. Diba also writes, "...equivalence of the dates is at variance with Mossadegh's own hand-written version, because the base date of 29 Rajab 1299 (Ghamari / lunar year), when correctly calculated, gives the Gregorian and Iranian (solar) calendar dates given here", meaning Friday June 16, 1882 or the date of 26 Khordad 1261 (Iranian Solar Calendar).

Since the date of 29 Rajab 1299 appears in both Mossadegh's note and Farhad Diba's discussion of the issue, one can determine that this is the correct date. The Islamic calendar was probably used more commonly in Iran during the period and the date written in Koran could have been only of this nature. 

We conclude that by all accounts the correct date of the birth of Dr. Mohammad Mossadegh is 29th of Rajab 1299 (Islamic Lunar Calendar) corresponding to 26 Khordad 1261 (Iranian Solar Calendar) or Friday June 16, 1882.