Al-Salâm `Alaykum wa Rahmah Allah wa Barakâtuh.
The Prophet (peace be upon him) was born in the same year that the Battle of the Elephant took place. None of his biographers differ on this matter. He was also most definitely born on a Monday. The Prophet (peace be upon him) said: “that was the day I was born and the day in which I was made a Prophet and the day in which revelation first came to me.” [Sahîh Muslim (1/819)]
The month and date of his birth, however, is a matter of disagreement. He may have been born on the twelth of Rabî` al-Awwal or the eighth of that month. Some say he was born in Ramadân. The least likely of all opinions is that he was born on the twenty-seventh of Rajab.
He died on a Monday, as stated by both Anas and `A’ishah. The year and month of his death are also known with certain. He died in 11 A.H. in the month of Rabî` al-Awwal.
About the date of his death, Ibn Hishâm writes:
They all agree that he died in Rabî` al-Awwal. Most of them say that it was on the twelfth of that month. However it could only have possibly been on the second, the thirteenth, the fourteenth, or the fifteenth.
The reason for this is the agreed upon fact that the Day of `Arafah during the farewell pilgrimage took place on a Friday, meaning that the ninth day of the month of Dhû al-Hijjah was on a Friday. This means that Dhû al-Hijjah began on a Thursday. This means that the following month, Muharram, started on either a Friday or a Saturday. If Muharram started on a Friday, then the month of Safar would have had to start on a Saturday or Sunday. Supposing that Safar started on a Saturday, then Rabî` al-Awwal could only have started on a Sunday or a Monday. Therefore, no matter how you calculated it, there is no way that the twelfth of Rabî` al-Awwal could have been on a Monday.
The Prophet (peace be upon him) was sixty-three years old when he died. This has been confirmed by a number of Companions, among them A’ishah and Ibn `Abbâs.
Source: Islam Today