Well, the Hijri date 12 Rajab 1366 corresponds to the Gregorian date Sunday, 1 June 1947. This date lies in the seventh month of the Hijri year 1366 AH, which is Rajab of 1366 AH. Both this Hijri and Gregorian date occur on the single day that is Sunday without any doubt. The Arabic date 1366/07/12 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 1 June 1947 to its equivalent Arabic date.
The following is the conversion of the Arabic date 12 Rajab 1366 AH to its equivalent Gregorian date.
فَذَرْهُمْ حَتَّىٰ يُلَٰقُوا۟ يَوْمَهُمُ ٱلَّذِى فِيهِ يُصْعَقُونَ
Then let them be (O Muhammad), till they meet their day, in which they will be thunder-stricken,
Surah At-Tur(52:45)