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. May 19, 1882 also appears in different writings. Yet our conclusion is that Mossadegh was actually born nearly a month later.

In his handwritten note shown here, 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 with today's digital 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, Mossadegh's nephew Farhad Diba arrives at a more divergent date: 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."