Ramadan date: why the Islamic calendar changes every year

Ramadan is the ninth month of the Islamic calendar. Unlike the Gregorian calendar used internationally, which is based on the cycle of the sun (365 days), the Muslim calendar relies exclusively on the cycles of the moon. Since a lunar year has approximately eleven fewer days than a solar year, the holy month mechanically moves forward by more than a week and a half every year on our civil calendar.

Beginning of Ramadan: lunar observation at the heart of geographical variations

In addition to this annual shift, the exact start of fasting may also differ from one country to another in the same year. The beginning of the holy month is strictly determined by the appearance of the new crescent moon in the night sky.

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Depending on the region, religious authorities rely on traditional visual observation with the naked eye, modern astronomical calculations, or choose to align themselves with announcements from other reference countries (as is the case with Muslims in the United Kingdom, who generally follow the guidelines of Morocco or Saudi Arabia). This explains why Muslims around the world may begin fasting one or two days apart.