Well, the Hijri date 15 Rajab 1338 corresponds to the Gregorian date Sunday, 4 April 1920. This date lies in the seventh month of the Hijri year 1338 AH, which is Rajab of 1338 AH. Both this Hijri and Gregorian date occur on the single day that is Sunday without any doubt. The Arabic date 1338/07/15 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 4 April 1920 to its equivalent Arabic date.
The following is the conversion of the Arabic date 15 Rajab 1338 AH to its equivalent Gregorian date.
فَإِنْ خِفْتُمْ فَرِجَالًا أَوْ رُكْبَانًۭا ۖ فَإِذَآ أَمِنتُمْ فَٱذْكُرُوا۟ ٱللَّهَ كَمَا عَلَّمَكُم مَّا لَمْ تَكُونُوا۟ تَعْلَمُونَ
And if ye go in fear, then (pray) standing or on horseback. And when ye are again in safety, remember Allah, as He hath taught you that which (heretofore) ye knew not.
Surah Al-Baqara(2:239)