Some deviant and ignorant people claim that the exact date of birth of the Prophet (SallAllaho Alaihi wa Aalihi wa Sallam) is not known and hence there is little room for the celebration of Eid-e-Milad-un-Nabi (SallAllaho Alaihi wa Aalihi wa Sallam) on 12th of Rabi' al-Awwal Sharif.

12 Rabi' al-Awwal is not only accepted as Milad Day from the classical and ancient scholars, it is also confirmed by the governments of the whole Islamic world. Almost three (3) dozen Islamic countries celebrate it and have public holidays on 12th of Rabi' al-Awwal Sharif.
 
1. Ibn-e-Ishaq (85-151 H):

 

Messenger of Allah (SallAllaho Alaihi wa Aalihi wa Sallam) was born on 12 Rabi' al-Awwal in 'Aam al-Feel. [Ibn Jawzi in al-Wafa, Page 87]
 

2. Allama Ibn Hisham (213 H):

 

Messenger of Allah (SallAllaho Alaihi wa Aalihi wa Sallam) was born on Monday 12 Rabi' al-Awwal in 'Aam al-Feel. [Ibn Hisham in As-Sirat-un-Nabawiya, Vol. 1, Page 158]
 

3. Imam Ibn Jarir Tabari (224-310 H):

 

Messenger of Allah (SallAllaho Alaihi wa Aalihi wa Sallam) was born on Monday 12 Rabi' al-Awwal in 'Aam al-Feel. [Tarikh al-Umam wa al-Muluk, Vol. 2, Page 125]
 

4. Allama Abu al-Hasan Ali bin Muhammad Al-Mawardi (370-480 H):

 

Messenger of Allah (SallAllaho Alaihi wa Aalihi wa Sallam) was born 50 days after the event of Ashab-ul-Feel and after the death of His father on Monday 12 Rabi' al-Awwal. [Ailam-un-Nabuwwa, Page 192]
 

5. Imam Al-Hafiz Abu-ul-Fatah Al-Undalasi (671-734 H):

 

Our leader and our Prophet Muhammad (SallAllaho Alaihi wa Aalihi wa Sallam), the Messenger of Allah, was born on Monday 12 Rabi' al-Awwal in 'Aam al-Feel. [Aayun al-Asr, Vol. 1, Page 33]
 

6. Allama Ibn Khaldun (732-808 H):

 

Messenger of Allah (SallAllaho Alaihi wa Aalihi wa Sallam) was born on 12 Rabi' al-Awwal in 'Aam al-Feel. It was the 40th year of Emperor Kasra Noshairwan. [Ibn Khaldun in At-Tarikh Vol. 2, Page 394]
 

7. Muhammad As-Sadiq Ibrahim Arjoon:

 

From various turaq (chains) it has been established as true that the Prophet (SallAllaho Alaihi wa Aalihi wa Sallam) was born on Monday 12 Rabi' al-Awwal in 'Aam al-Feel in the reign of Kisra Noshayrwan. [Muhammad Rasoolullah, Vol. 1, Page 102]
 

8. Shaykh Abdul-Haq Muhadath Dehlvi (950-1052 H):

 

Know it well, that over-whelming majority of the experts of sayar and tarikh (i.e. biographers and historians) hold the opinion that the Beloved (i.e. the Prophet SallAllaho Alaihi wa Aalihi wa Sallam) was born in 'Aam al-Feel … It is well known that the month was of Rabi' al-Awwal and its date was 12. Various scholars have shown their agreement with this (date). [Madarij-un-Nabuwwah, Vol. 2, Page 14]
 

9. Imam Qustallani (Alaihir RaHma) said:

 

Rasoolullah (SallAllaho Alaihi wa Sallam) was born on 12th Rabi ul Awwal and People of Makkah follow it, on this same day they visit (your place of birth).. It is famous that you were born on 12th Rabi ul Awwal, the day was of Monday, Ibn Ishaq and others have narrated this too. [Al Muwahib al Laduniya, Vol. 1, Page 88]
 

Now we will prove from scholars whom even Wahabi/Salafis consider the top most scholar in Tafsir and Tarikh and they not only say 12th is the mainstream opinion but also rely with exact hadith for it:

10. Ibn Kathir writes in his Seerat un-Nabi:

ورواه ابن أبى شيبة في مصنفه عن عفان ، عن سعيد بن ميناء ، عن جابر وابن عباس أنهما قالا : ولد رسول الله صلى الله عليه وسلم عام الفيل يوم الاثنين الثانى عشر من شهر ربيع الاول
Ibn Abi Shaybah in his Musannaf narrates from Affan, Sa’id, Jabir and Ibn Abbas (Ridwanullahi Ta'ala Alaihim Ajma'een) who said: Rasoolullah (SallAllaho Alaihi wa Sallam) was born in the year of elephant on Monday, the 12th Rabi al-Awwal [Seerat un-Nabi, Volume 1, Page No. 199]

Then he said:

وهذا هو المشهور عند الجمهور والله أعلم
This is what is famous amongst Majority and Allah knows the best

11. Nawab Muhammad Sadiq Hasan Khan Bohapali:

 

The birth (of the Prophet SallAllaho Alaihi wa Aalihi wa Sallam) was happened in Mecca at the time of Fajar on Monday 12 Rabi' al-Awwal in 'Aam al-Feel. Majority of scholars holds this opinion. Ibn-e-Jawzi has narrated a consensus (of scholars) on it. [Ash-Shumamat al-Anbariya fi Mawlid Khair al-Bariyyah, Page 7]
 

You can see that the historians / scholars from the first / second century of Hijri, as well as the scholars of later times, had been authenticating it. The list also includes the well known leader of Salafis, i.e. Nawab Sadiq Hasan Bohapalvi.
 
Milad-un-Nabi (SallAllaho Alaihi wa Aalihi wa Sallam) is celebrated throughout the Islamic world, with the exception of a few countries. Interestingly, most of the Muslim countries and few non-Muslim countries celebrate it on 12th of Rabi' al-Awwal.

Here is a list of few countries who hold an official holiday on 12th of Rabi' al-Awwal (the actual list is longer than this):

Islamic Countries:

 

* Islamic Republic of Pakistan
* Afghanistan
* Uzbekistan
* Jordan
* United Arab Emirates (U.A.E.)
* Bahrain
* Bangladesh
* Algeria
* Al-Jazair
* Sudan
* Iraq
* Kuwait
* Morocco
* Yemen
* Tunis
* Syria
* Oman
* Lebanon
* Libya
* Egypt
* Moritaniya
* Palestine
* Brunei
* Indonesia
* Malaysia
* Nigeria
* Somalia
* Turkey (not a public holiday, but mosques are illuminated, special foods and treats are prepared, and you can participate, actively or passively, in the celebrations)
 

Non-Islamic Countries:

 

* India
* Sri Lanka
* Tanzania
 

The most authentic date of Milad-un-Nabi (i.e. Prophet SallAllaho Alaihi wa Aalihi wa Sallam's birth), as agreed upon by the classical and later scholars and historians, and as officially recognized by Islamic countries, is Monday 12 Rabi' al-Awwal.

Allah SubHanuhu wa Ta'ala and His Beloved Messenger Knows the Best!!