Opinion of Renowned Historians for Authentic Date of Milad E Mustafa صلی اللہ علیہ وسلم

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-e-Hasham (213 H): 

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

3. Imam Ibn-e-Jareer 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-ul-Umam-wal-Muluk,Vol. 2, Page 125)

4. Allama Abul 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-e-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-e-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 Kasara Noshairwan. (Muhammad Rasoolullah, Vol. 1, Page 102)

8. Sheikh 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 Qastallani (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, Volume 1, Page No. 88)

Now I am going to prove from scholars whom even Wahabi/Salafis consider the top most scholar in Tafsir and Tarikh and he not only says 12th is the mainstreem opinion but also relies with exact hadith for it:

1. Ibn Kathir write 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 Ul 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 [ibid]

2. Nawab Muhammad Sadiq Hasan Khan Bohapalvi:

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-Shumama-tul-Anbariya Fi Mowlid Khair al-Bariyya, 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.