Well, the Hijri date 21 Jumada Al Oula 1399 corresponds to the Gregorian date Wednesday, 18 April 1979. This date lies in the fifth month of the Hijri year 1399 AH, which is Jumada Al-Awwal of 1399 AH. Both this Hijri and Gregorian date occur on the single day that is Wednesday without any doubt. The Arabic date 1399/05/21 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 18 April 1979 to its equivalent Arabic date.
The following is the conversion of the Arabic date 21 Jumada Al Oula 1399 AH to its equivalent Gregorian date.
قَالُوٓا۟ إِنْ هَٰذَٰنِ لَسَٰحِرَٰنِ يُرِيدَانِ أَن يُخْرِجَاكُم مِّنْ أَرْضِكُم بِسِحْرِهِمَا وَيَذْهَبَا بِطَرِيقَتِكُمُ ٱلْمُثْلَىٰ
They said: Lo! these are two wizards who would drive you out from your country by their magic, and destroy your best traditions;
Surah Taa-Haa(20:63)
Sahih al-Bukhari
Penalty of Hunting while on Pilgrimage
Chapter: Performing Hajj for a person who cannot sit firmly on the mount
Narrated `Abdullah bin `Abbas:
Al-Fadl was riding behind the Prophet (ﷺ) and a woman from the tribe of Khath'am came up. Al-Fadl started looking at her and she looked at him. The Prophet (ﷺ) turned Al-Fadl's face to the other side. She said, "My father has come under Allah's obligation of performing Hajj but he is a very old man and cannot sit properly on his Mount. Shall I perform Hajj on his behalf? The Prophet (ﷺ) replied in the affirmative. That happened during Hajjat-al-Wada` of the Prophet (ﷺ) .
Sahih al-Bukhari 1854