Well, the Hijri date 18 Dhul Qidah 1405 corresponds to the Gregorian date Sunday, 4 August 1985. This date lies in the eleventh month of the Hijri year 1405 AH, which is Dhu Al-Qidah of 1405 AH. Both this Hijri and Gregorian date occur on the single day that is Sunday without any doubt. The Arabic date 1405/11/18 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 August 1985 to its equivalent Arabic date.
The following is the conversion of the Arabic date 18 Dhul Qidah 1405 AH to its equivalent Gregorian date.
ذَٰلِكَ بِأَنَّهُۥ كَانَت تَّأْتِيهِمْ رُسُلُهُم بِٱلْبَيِّنَٰتِ فَقَالُوٓا۟ أَبَشَرٌۭ يَهْدُونَنَا فَكَفَرُوا۟ وَتَوَلَّوا۟ ۚ وَّٱسْتَغْنَى ٱللَّهُ ۚ وَٱللَّهُ غَنِىٌّ حَمِيدٌۭ
That was because their messengers (from Allah) kept coming unto them with clear proofs (of Allah's Sovereignty), but they said: Shall mere mortals guide us? So they disbelieved and turned away, and Allah was independent (of them). Allah is Absolute, Owner of Praise.
Surah At-Taghaabun(64:6)