About the Hijri calendar

The Hijri (Islamic) calendar is a lunar calendar of 12 months, each beginning with the sighting of the new crescent moon. A Hijri year is about 354 days — roughly 11 days shorter than the solar Gregorian year — which is why Ramadan and the two Eids move earlier through the seasons each year. The calendar counts from the Prophet Muhammad's migration (Hijra) from Mecca to Medina in 622 CE, so the current year is written with the suffix "AH" (Anno Hegirae).

The months alternate between 29 and 30 days, and an extra day is added to the final month, Dhul-Hijjah, in leap years. Because the calendar depends on the moon, the exact start of a month can vary by a day between countries that rely on physical moon-sighting and those that use astronomical calculation, such as Saudi Arabia's Umm al-Qura calendar used on this page.