The Official Umm al-Qura Calendar
For daily civil affairs, government operations, and business scheduling, Saudi Arabia relies on the Umm al-Qura calendar. This calendar is prepared by the Institute of Astronomical and Geophysical Research at King Abdulaziz City for Science and Technology (KACST) in Riyadh.
The calendar calculates the start of each lunar month using the astronomical coordinates of the Holy Kaaba in Makkah. If the moon sets after sunset on the 29th day of the current lunar month, the new month begins the following morning. This provides a highly reliable, mathematically consistent civil calendar for the entire country.
How the Supreme Court Verifies Holy Months
While the Umm al-Qura calendar serves as the administrative baseline throughout the year, Saudi Arabia maintains the sacred prophetic tradition of physical moon sighting for religious months.
Before the start of Ramadan, Shawwal (Eid al-Fitr), and Dhul Hijjah (Hajj), the Supreme Court of Saudi Arabia (المحكمة العليا) officially calls upon Muslims across the country to sight the new crescent moon on the evening of the 29th. Official astronomical observatories with clear desert atmospheres — notably at Sudair and Tumair — work alongside certified judicial observers. Once testimonies are formally verified by the courts, the Supreme Court issues the royal announcement confirming the beginning of the holy month.
When Does the Date Change Each Day?
In Islamic tradition, the day begins at sunset (Maghrib prayer) rather than at midnight. When the Maghrib Adhan is called from the minarets of the Grand Mosque in Makkah, Muslims enter the evening of the next Islamic date. However, for digital clocks, public offices, and administrative records, the calendar advances at local midnight (12:00 AM) in the Asia/Riyadh (UTC+3) time zone.