Well, the Hijri date 21 Rabi Al Awwal 1191 corresponds to the Gregorian date Monday, 28 April 1777. This date lies in the third month of the Hijri year 1191 AH, which is Rabi Al-Awwal of 1191 AH. Both this Hijri and Gregorian date occur on the single day that is Monday without any doubt. The Arabic date 1191/03/21 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 28 April 1777 to its equivalent Arabic date.
The following is the conversion of the Arabic date 21 Rabi Al Awwal 1191 AH to its equivalent Gregorian date.
أَوْ تَقُولَ لَوْ أَنَّ ٱللَّهَ هَدَىٰنِى لَكُنتُ مِنَ ٱلْمُتَّقِينَ
Or should say: If Allah had but guided me I should have been among the dutiful!
Surah Az-Zumar(39:57)