The date of Muhammad's birth is a matter of contention since the exact date is unknown and isn't definitively recorded in the Islamic traditions.
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3rd Hijri Month: When Is Rabi-al-Awwal 2017 (1439)?

Science Section Staff
17 November, 2017

Rabi-al-Awwal is the 3rd month in the Hijri calendar. During this month, the Muslims celebrate the birthday of Prophet Muhammad (PBUH).

The exact birthdate is unknown. However, the majority of Muslims believe it to be on the 12th of this month. Whereas a minority of Muslims believe it to be on the 17th.

The Hijri calendar is a lunar one. Its months begin when the first crescent of a new moon is sighted. The Hijri lunar calendar year is 11 to 12 days shorter than the solar year. Thus, Rabi-al-Awwal and Hijri months migrates throughout the seasons.

Astronomical Observation

The Astronomical New Moon (conjunction) is on Saturday, November 18, 2017 at 11:42 UT. On that day, telescopes in North America can observe the moon.

Rabi-al-Awwal 1439

Then, on November 19, the crescent can be seen in Africa and Americas, and with difficulty in parts of Asia and Europe.

Rabi-al-Awwal 1439

On November 20, it will be easily visible everywhere in the world. Dr. Hatem Ouda, the head of the Egypt’s National Research Institute of Astronomy and Geophysics (NRIAG) announced that Rabi-al-Awwal 1439 will start on Sunday the 19th.

Rabi-al-Awwal 1439

This means that the Mawlid of Prophet Muhammad (Peace and Blessings be Upon Him) will be on Thursday the 30th of November 2017.