The Umm al-Qura Calendar is a calculated lunar Hijri calendar published in advance and used as the official civil dating reference in Saudi Arabia. It displays Hijri dates with their Gregorian equivalents and supports official transactions, government services, and date conversion.

Calling it calculated does not make it a substitute for every religious announcement. The beginnings of Ramadan, Shawwal, and Dhu al-Hijjah, and the acts of worship connected to them, remain subject to the competent authorities and official announcements.

The first issue of the Umm al-Qura Calendar was published in 1346 AH by the Government Press in Makkah. Printing later moved to Riyadh in 1399 AH, and a scientific supervisory committee with specialists in Islamic law and astronomy was formed in 1400 AH.

Since 1420 AH, the coordinates of the Kaaba in Makkah have served as the reference for the astronomical calculations associated with the calendar, alongside ongoing development of its data and criteria.

The process begins by calculating astronomical conjunction, the moment at which the Moon completes its conjunction cycle with the Sun and the new lunar month is born astronomically. The relationship between sunset and moonset in Makkah is then assessed and the adopted civil-calendar rule is applied.

When the start-of-month conditions are met, the following day is listed as the first day of the new Hijri month. Otherwise, the current month continues until its calculated length is complete; a month has 29 or 30 days.

1. Calculate the time of astronomical conjunction.

2. Calculate sunset and moonset in Makkah and compare them.

3. Apply the Umm al-Qura criterion to the astronomical results.

4. Prepare annual tables showing Hijri dates and their Gregorian equivalents.

5. Defer to official announcements when a religious observance cannot be determined by the civil table alone.

Example of a month start: if conjunction occurs before sunset and the Moon sets after the Sun in Makkah under the adopted conditions, the next day may be listed as the first day of the new month. This illustrates the mechanism and is not an announcement for a specific month.

Example of calculation versus announcement: the table may list an expected first day of Ramadan, while the official announcement may set it one day differently after the relevant legal and observational process.

Example of conversion: entering a Hijri date in Miqat with “Umm al-Qura” selected returns its Gregorian equivalent from the same civil method. An approximate astronomical method may differ for some months.

The calendar is used for civil dating, government transactions, contracts, digital services, Hijri–Gregorian conversion, annual schedules, and advance presentation of Hijri occasions.

For observances that depend on the official determination of a new month, the calculated date should be treated as a civil reference or expectation, while the competent authority’s announcement remains decisive.

Umm al-Qura is not a simple fixed tabular lunar calendar. It is based on astronomical criteria associated with Makkah, and details may change when its standards or data are updated. A precomputed astronomical date is not necessarily identical to visual crescent sighting everywhere.

Miqat identifies the Umm al-Qura method clearly and provides an astronomical comparison when useful. For official religious use, the competent authority’s announcement remains final.