Future Saudi Eid al-Adha dates are estimated using which calendar?

Future Saudi Eid al-Adha dates are estimated using the Umm al-Qura calendar. Saudi Arabia uses this calculated lunar calendar for administrative planning, allowing dates to be projected years ahead rather than waiting for a final announcement.

Eid al-Adha falls on 10 Dhu al-Hijjah, the twelfth month of the Islamic calendar. Because the Hijri year is about 10–11 days shorter than the Gregorian year, the festival moves earlier through the solar calendar each year. The Umm al-Qura system uses astronomical calculations to estimate the starts of lunar months.

A common mix-up is treating the estimate as universally final. Saudi religious authorities traditionally confirm Dhu al-Hijjah through the kingdom’s moon-sighting process, and other countries may follow their own observations or calculations. Consequently, Eid can begin on different Gregorian dates in different places.

The Julian calendar is a solar calendar, the Hebrew calendar is lunisolar, and the tabular Islamic calendar is a separate calculated model. None is the named Saudi reference for projected Eid al-Adha dates.