Well, the Hijri date 12 Rabi Al Thani 1399 corresponds to the Gregorian date Saturday, 10 March 1979. This date lies in the fourth month of the Hijri year 1399 AH, which is Rabi Al-Thani of 1399 AH. Both this Hijri and Gregorian date occur on the single day that is Saturday without any doubt. The Arabic date 1399/04/12 is calculated using the Umm Al-Qura calendar and the sighting of the moon. One thing to remember is that this Arabic date may occur on different Gregorian date depending upon the region and country and obviously the moon.
If you are still not sure about the date then you can use our Arabic date converter.
The following is the conversion of the Gregorian date 10 March 1979 to its equivalent Arabic date.
The following is the conversion of the Arabic date 12 Rabi Al Thani 1399 AH to its equivalent Gregorian date.
وَمَنْ أَظْلَمُ مِمَّنِ ٱفْتَرَىٰ عَلَى ٱللَّهِ ٱلْكَذِبَ وَهُوَ يُدْعَىٰٓ إِلَى ٱلْإِسْلَٰمِ ۚ وَٱللَّهُ لَا يَهْدِى ٱلْقَوْمَ ٱلظَّٰلِمِينَ
And who doeth greater wrong than he who inventeth a lie against Allah when he is summoned unto Al-Islam? And Allah guideth not wrongdoing folk.
Surah As-Saff(61:7)
Sahih al-Bukhari
The Two Festivals (Eids)
Chapter: The Khutba after the Eid prayer
Narrated Ibn `Umar:
Allah's Messenger (ﷺ), Abu Bakr and `Umar! used to offer the two `Id prayers before delivering the Khutba.
Sahih al-Bukhari 963