The Islamic (Hijri) calendar is purely lunar: twelve months of 29 or 30 days, each beginning with the sighting of the new crescent moon. A lunar year is around 10–12 days shorter than a solar year, which is why Ramadan, the Hajj season and the two Eids drift earlier through the seasons — a fast that falls in short, cool December days one decade arrives in long summer days the next.

Why certain days matter

Beyond the major months, the calendar carries a rhythm of recommended worship: the white days (13th, 14th and 15th of each month) when fasting is encouraged, the day of Arafah, the day of Ashura in Muharram, and the first ten days of Dhul Hijjah. This calendar highlights those days so they are noticed in time to act on them, not remembered afterwards.

Why dates sometimes differ in the UK

UK communities follow different approaches to confirming the new month — local or regional moonsighting, reports from Morocco or South Africa, or astronomical calculation. That is why neighbouring mosques occasionally begin Ramadan or celebrate Eid a day apart. The dates shown here follow one consistent convention; treat your local mosque's announcement as the final word for acts of worship tied to a specific day.

Use the calendar to look ahead: plan the white days into your month, note when the sacred months begin, and give yourself time to prepare for Ramadan rather than meeting it unprepared.