Well, the Hijri date 13 Rabi Al Awwal 1399 corresponds to the Gregorian date Saturday, 10 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 Saturday without any doubt. The Arabic date 1399/03/13 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 10 February 1979 to its equivalent Arabic date.
The following is the conversion of the Arabic date 13 Rabi Al Awwal 1399 AH to its equivalent Gregorian date.
فَإِذَا فَرَغْتَ فَٱنصَبْ
So when thou art relieved, still toil
Surah Ash-Sharh(94:7)
Sahih al-Bukhari
Knowledge
Chapter: To give a religious verdict while riding an animal or standing on anything else
Narrated `Abdullah bin `Amr bin Al `Aas:
Allah's Messenger (ﷺ) stopped (for a while near the Jimar) at Mina during his last Hajj for the people and they were asking him questions. A man came and said, "I forgot and got my head shaved before slaughtering the Hadi (sacrificing animal)." The Prophet (ﷺ) said, "There is no harm, go and do the slaughtering now." Then another person came and said, "I forgot and slaughtered (the camel) before Rami (throwing of the pebbles) at the Jamra." The Prophet (ﷺ) said, "Do the Rami now and there is no harm." The narrator added: So on that day, when the Prophet (ﷺ) was asked about anything (as regards the ceremonies of Hajj) performed before or after its due time, his reply was: "Do it (now) and there is no harm."
Sahih al-Bukhari 83