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🌓 How the Islamic (Hijri) Calendar Works
Every year, Ramadan and Eid fall about 10–11 days earlier on the Gregorian calendar than the year before. This isn't random — it's a direct result of how the Islamic calendar is structured.
Lunar vs Solar Calendar
The Gregorian calendar most of the world uses is solar, based on Earth's orbit around the sun (365.25 days). The Hijri calendar is purely lunar, based on the moon's cycle around the Earth, making a Hijri year roughly 354–355 days — about 10–11 days shorter than a solar year.
Why Ramadan Shifts Every Year
Because the Hijri year is shorter, Islamic months — including Ramadan — drift backward through the Gregorian calendar by about 10–11 days annually, completing a full cycle through all four seasons roughly every 33 years.
Role of Moon-Sighting Committees
Each Hijri month begins with the sighting of the new crescent moon (hilal). Local or national moon-sighting committees observe the sky and make an official announcement, which is why the exact start of Ramadan or Eid can sometimes differ by a day between countries.
Umm al-Qura Calendar Explained
The Umm al-Qura Calendar, published by the Kingdom of Saudi Arabia, uses precise astronomical calculations to project Islamic dates in advance, and is the most widely referenced calendar for planning purposes — including the projected dates shown on EidClock. Final confirmation always still comes from actual moon sighting.