There are some similarities between the old Muhammedan Calendar and Umar's Hijri Calendar visible even today despite some position changes. For example the month names: Sivan/Ṣafar, Elul/alŪlā, Cheshvan/Shaʿbān, and Shevat/Shawwāl. Also, the major Hajj of the year is in the originally spring month of Dhū al-Ḥijja exactly like Passover in Aviv (spring). This is followed by the fasting of Iyyar/Muḥarram commemorating the deliverance from Egypt. Finally of course and Moreover, the 7th month is still sacred in both. Finally, Ramadan corresponded to the old Julian Calendar's month of December of course.