Praise be to Allah.

Firstly: 

The biographers and historians differed concerning the day and month of the birth of the Prophet (blessings and peace of Allah be upon him). This is something for which there is good reason, as it was not known what status this newborn would achieve; his situation was like that of any other newborn. Hence no one can state with certainty the date of his birth (blessings and peace of Allah be upon him). 

Dr. Muhammad at-Tayyib an-Najjaar (may Allah have mercy on him) said: 

Perhaps the reason for this difference of opinion is that when he was born, no one expected that he would attend such a status. For that reason, he did not live in the spotlight from the beginning of his life. When Allah decreed that the Messenger (blessings and peace of Allah be upon him) should begin to convey His message forty years after he was born, people began to seek out whatever memories they had about this Prophet, and they asked one another about every detail of his life. They were helped in that by what the Messenger (blessings and peace of Allah be upon him) himself narrated about incidents that he had experienced from his birth, as well as the reports narrated by his Companions and those who had also gone through those events with him. 

At that time the Muslims began to collect everything that they had heard about the life story of their Prophet (blessings and peace of Allah be upon him) in order to transmit it to the people down throughout the ages 

Al-Qawl al-Mubeen fi Seerat Sayyid al-Mursaleen, p. 78 

Secondly: 

Among the matters on which there is consensus with regard to his birth (blessings and peace of Allah be upon him) is the definition of the year and the day. 

1.With regard to the year:

It was the Year of the Elephant. Ibn al-Qayyim (may Allah have mercy on him) said: 

There is no difference of opinion concerning the fact that he (blessings and peace of Allah be upon him) was born in Makkah, and that his birth was in the Year of the Elephant. 

Zaad al-Ma‘aad fi Hadiy Khayr al-‘Ibaad, 1/76 

Muhammad ibn Yoosuf as-Saalihi (may Allah have mercy on him) said: 

Ibn Ishaaq (may Allah have mercy on him) said: (It was) the Year of the Elephant. 

Ibn Katheer said: This is the well-known view of the majority. 

Ibraaheem ibn al-Mundhir al-Hizaami, the Shaykh of al-Bukhaari, said: This is the opinion concerning which none of the scholars has any doubt. Khaleefah ibn Khayyaat, Ibn al-Jazzaar, Ibn Dihyah, Ibn al-Jawzi and Ibn al-Qayyim went further and narrated that there was consensus on this matter. 

Subul al-Huda wa’r-Rashaad fi Seerat Khayr al-‘Ibaad, 1/334, 335 

Dr. Akram Diya’ al-‘Umari (may Allah guide him) said: 

In fact the reports that say otherwise all have flawed isnaads; they suggest that he was born ten years, or twenty-three years, or forty years, after the Year of the Elephant. But the majority of scholars are of the view that he was born in the Year of the Elephant. This is supported by the modern study undertaken by both Muslim and Orientalist researchers who stated that the Year of the Elephant corresponds to the year 570 CE or 571 CE. 

As-Seerah an-Nabawiyyah as-Saheehah, 1/97 

2.With regard to the day:

It was a Monday. He (blessings and peace of Allah be upon him) was born on a Monday, his mission began on a Monday and he died on a Monday. 

It was narrated that Abu Qataadah al-Ansaari (may Allah have mercy on him) said: The Prophet (blessings and peace of Allah be upon him) was asked about fasting on Mondays and he said: “That is a day on which I was born and on it my mission began – or Revelation came to me.”

Narrated by Muslim, 1162. 

Ibn Katheer (may Allah have mercy on him) said: 

Those who say that he was born on Friday 17^th Rabee‘ al-Awwal were mistaken. 

This was narrated by al-Haafiz Ibn Dihyah from what he read [?] of the book I‘laam ar-Wara bi A‘laam al-Huda by one of the Shi‘ah. Then Ibn Dihyan stated why it was da‘eef (weak), and it deserves to be classed as da‘eef because it is contrary to the text. 

As-Seerah an-Nabawiyyah, 1/199 

Thirdly: 

With regard to the point on which there is scholarly disagreement, that has to do with defining the month and the day of the month. We have come across many opinions concerning that, including the following: 

1.That he was born on 2^nd Rabee ‘ al-Awwal.

Ibn Katheer (may Allah have mercy on him) said: 

It was said that he was born on the second of the month. This was stated by Ibn ‘Abd al-Barr in al-Isti‘aab, and was narrated by al-Waaqidi from Abu Ma‘shar Nujayh ibn ‘Abd ar-Rahmaan al-Madani. 

As-Seerah an-Nabawiyyah, 1/199 

2.It was said that he was born on 8^th Rabee‘ al-Awwal.

Ibn Katheer (may Allah have mercy on him) said: 

It was said that he was born on the eighth of the month. This was narrated by al-Humaydi from Ibn Hazm, and was narrated by Maalik, ‘Aqeel, Yoonus ibn Yazeed and others from az-Zuhri from Muhammad ibn Jubayr ibn Mut‘im. Ibn ‘Abd al-Barr narrated that the historians regarded it as saheeh; it was stated definitively by al-Haafiz al-Kabeer Muhammad ibn Moosa al-Khawaarizmi, and was regarded as most likely to be correct by al-Haafiz Abu’l-Khattaan ibn Dihyah in his book at-Tanweer fi Mawlid al-Basheer an-Nadheer. 

As-Seerah an-Nabawiyyah, 1/199 

3.It was said that he was born on 10^th Rabee ‘ al-Awwal.

Ibn Katheer (may Allah have mercy on him) said: 

It was said that he was born on the tenth of the month. This was narrated by Ibn Dihyah in his book, and was narrated by Ibn ‘Asaakir from Abu Ja‘far al-Baaqir. It was also narrated by Mujaalid from ash-Sha‘bi. 

As-Seerah an-Nabawiyyah, 1/199 

4.It was said that he was born on 12^th Rabee ‘ al-Awwal.

Ibn Katheer (may Allah have mercy on him) said: 

It was said that he was born on the twelfth of the month. This was stated by Ibn Ishaaq. It was narrated by Ibn Abi Shaybah in his Musannaf from ‘Affaan from Sa‘eed ibn Meena’ that Jaabir and Ibn ‘Abbaas said: The Messenger of Allah (blessings and peace of Allah be upon him) was born in the Year of the Elephant on Monday 12^th Rabee‘ al-Awwal; on Monday his mission began, on Monday he was taken up to heaven, on Monday he migrated, and on Monday he died.

This is the well-known opinion according to the majority. And Allah knows best. 

As-Seerah an-Nabawiyyah, 1/199 

It was also said that he was born in Ramadan or in Safar or some other month. 

What appears to us to be the case is that the strongest opinion concerning the birth of the Prophet (blessings and peace of Allah be upon him) is that he was born between the eighth and the twelfth of Rabee‘ al-Awwal. Some Muslim mathematicians and astronomers have determined that the Monday in question was the ninth of Rabee‘ al-Awwal. It may be that this is another opinion, and it has some merit. That corresponds to 20^th April 571 CE. This is what the authors of some modern books on Seerah (Prophet’s biography) regard as most likely to be correct, including Professor Muhammad al-Khudari and Safi ar-Rahmaan al-Mubaarakfoori. 

Abu’l-Qaasim as-Suhayli (may Allah have mercy on him) said: 

The mathematicians say that his birth occurred in the solar month of April, on the twentieth of that month. 

Ar-Rawd al-Unuf, 1/282 

Prof. Muhammad al-Khudari (may Allah have mercy on him) said: 

The Egyptian astronomer Mahmoud Basha (d. 1885 CE) who was well-versed in astronomy, geography and mathematics, and wrote several books based on his research stated that it was on the morning of Monday 9^th Rabee‘ al-Awwal, which corresponds to 20^th April 571 CE. That corresponds to the first year following the elephant incident. He was born in the house of Abu Taalib in Shi‘ab Banu Haashim. 

Noor al-Yaqeen fi Seerat Sayyid al-Mursaleen (p. 9). See also ar-Raheeq al-Makhtoom (p. 41). 

Fourthly: 

With regard to the date of the death of our Prophet Muhammad (blessings and peace of Allah be upon him), there is no difference of opinion concerning the fact that it occurred on a Monday. The report narrated from Ibn Qutaybah, saying that it occurred on a Wednesday, is not correct. Perhaps what he meant is that the Prophet (blessings and peace of Allah be upon him) was buried on Wednesday, which is correct. 

With regard to the year of his death, there is no difference of opinion concerning the fact that it was in 11 AH. 

With regard to the month of his death, there is no difference of opinion concerning the fact that it was in Rabee‘ al-Awwal. 

With regard to the date of his death in that month, there is a difference of opinion among the scholars. 

1.The majority are of the view that it occurred on 12^th Rabee‘ al-Awwal.

2.al-Khawaarizmi was of the view that it occurred on 1^st Rabee‘ al-Awwal.

3.Ibn al-Kalbi and Abu Makhnaf were of the view that it occurred on 2^nd Rabee‘ al-Awwal. As-Suhayli was inclined to favour this view and al-Haafiz Ibn Hajar (may Allah have mercy on him) regarded it as most likely to be correct.

The most well-known view is that of the majority, which is that the death of the Prophet (blessings and peace of Allah be upon him) occurred on 12^th Rabee‘ al-Awwal 11 AH. 

See ar-Rawd al-Unuf by as-Suhayli (4/439, 440); as-Seerah an-Nabawiyyah by Ibn Katheer (4/509); Fath al-Baari by Ibn Hajar (8/130). 

And Allah knows best.