Well, the Hijri date 21 Rabi Al Thani 1266 corresponds to the Gregorian date Tuesday, 5 March 1850. This date lies in the fourth month of the Hijri year 1266 AH, which is Rabi Al-Thani of 1266 AH. Both this Hijri and Gregorian date occur on the single day that is Tuesday without any doubt. The Arabic date 1266/04/21 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 5 March 1850 to its equivalent Arabic date.
The following is the conversion of the Arabic date 21 Rabi Al Thani 1266 AH to its equivalent Gregorian date.
إِنَّمَا ٱلْمُؤْمِنُونَ ٱلَّذِينَ ءَامَنُوا۟ بِٱللَّهِ وَرَسُولِهِۦ وَإِذَا كَانُوا۟ مَعَهُۥ عَلَىٰٓ أَمْرٍۢ جَامِعٍۢ لَّمْ يَذْهَبُوا۟ حَتَّىٰ يَسْتَـْٔذِنُوهُ ۚ إِنَّ ٱلَّذِينَ يَسْتَـْٔذِنُونَكَ أُو۟لَٰٓئِكَ ٱلَّذِينَ يُؤْمِنُونَ بِٱللَّهِ وَرَسُولِهِۦ ۚ فَإِذَا ٱسْتَـْٔذَنُوكَ لِبَعْضِ شَأْنِهِمْ فَأْذَن لِّمَن شِئْتَ مِنْهُمْ وَٱسْتَغْفِرْ لَهُمُ ٱللَّهَ ۚ إِنَّ ٱللَّهَ غَفُورٌۭ رَّحِيمٌۭ
They only are the true believers who believe in Allah and His messenger and, when they are with him on some common errand, go not away until they have asked leave of him. Lo! those who ask leave of thee, those are they who believe in Allah and His messenger. So, if they ask thy leave for some affair of theirs, give leave to whom thou wilt of them, and ask for them forgiveness of Allah. Lo! Allah is Forgiving, Merciful.
Surah An-Noor(24:62)