You will see in chapter=20 verse=59 a day called یوم الزینة mentioned in Qur'an:
قَالَ مَوْعِدُكُمْ يَوْمُ الزِّينَةِ وَأَن يُحْشَرَ النَّاسُ ضُحًى
[Moses] said, "Your appointment is on the day of the festival when the people assemble at mid-morning."
Is this a special day in Egyptian or Hebrew calendar? Or do you know an accurate date for this event in astronomy?