Jumu`ah prayer is when the sun has passed its zenith
وَحَدَّثَنَا يَحْيَى بْنُ يَحْيَى، وَإِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالاَ أَخْبَرَنَا وَكِيعٌ، عَنْ يَعْلَى بْنِ، الْحَارِثِ الْمُحَارِبِيِّ عَنْ إِيَاسِ بْنِ سَلَمَةَ بْنِ الأَكْوَعِ، عَنْ أَبِيهِ، قَالَ كُنَّا نُجَمِّعُ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم إِذَا زَالَتِ الشَّمْسُ ثُمَّ نَرْجِعُ نَتَتَبَّعُ الْفَىْءَ .
Iyas b. Salama b. al-Akwa' reported on the authority of his father: We used to observe the Friday prayer with the Messenger of Allah (ﷺ) when the sun passed the meridian. and we then returned and tried to find out afternoon shadow (of the walls for protecting themselves from the heat of the sun).