Well, the Hijri date 15 Rabi Al Awwal 1399 corresponds to the Gregorian date Monday, 12 February 1979. This date lies in the third month of the Hijri year 1399 AH, which is Rabi Al-Awwal of 1399 AH. Both this Hijri and Gregorian date occur on the single day that is Monday without any doubt. The Arabic date 1399/03/15 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 12 February 1979 to its equivalent Arabic date.
The following is the conversion of the Arabic date 15 Rabi Al Awwal 1399 AH to its equivalent Gregorian date.
قَدْ قَالَهَا ٱلَّذِينَ مِن قَبْلِهِمْ فَمَآ أَغْنَىٰ عَنْهُم مَّا كَانُوا۟ يَكْسِبُونَ
Surah Az-Zumar(39:50)
Sahih al-Bukhari
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
Chapter: The Ghazwa of Al-Khandaq or Al-Ahzab Battle
Narrated `Ali:
On the day of Al-Khandaq (i.e. Trench), the Prophet (ﷺ) said '(Let) Allah fill their (i.e. the infidels') houses and graves with fire just as they have prevented us from offering the Middle Prayer (i.e. `Asr prayer) till the sun had set."
Sahih al-Bukhari 4111