Well, the Hijri date 1 Rajab 1266 corresponds to the Gregorian date Sunday, 12 May 1850. This date lies in the seventh month of the Hijri year 1266 AH, which is Rajab of 1266 AH. Both this Hijri and Gregorian date occur on the single day that is Sunday without any doubt. The Arabic date 1266/07/01 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 12 May 1850 to its equivalent Arabic date.
The following is the conversion of the Arabic date 1 Rajab 1266 AH to its equivalent Gregorian date.
وَهُوَ ٱلَّذِى جَعَلَ لَكُمُ ٱلنُّجُومَ لِتَهْتَدُوا۟ بِهَا فِى ظُلُمَٰتِ ٱلْبَرِّ وَٱلْبَحْرِ ۗ قَدْ فَصَّلْنَا ٱلْءَايَٰتِ لِقَوْمٍۢ يَعْلَمُونَ
And He it is Who hath set for you the stars that ye may guide your course by them amid the darkness of the land and the sea. We have detailed Our revelations for a people who have knowledge.
Surah Al-An'aam(6:97)