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Date Converter
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Accurate Islamic Calendar Conversion
Knowledge
How It Works
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How Hijri-Gregorian Conversion Works
The Islamic (Hijri) calendar is purely lunar, meaning it is based entirely on the phases of the moon. A lunar year is typically 354 or 355 days long—about 11 days shorter than the solar Gregorian year. This is why Ramadan and other Islamic dates shift backward by approximately 11 days every year in the Gregorian calendar.
What is the difference between the Umm al-Qura calendar and local moon-sighting?
The Umm al-Qura calendar is a pre-calculated astronomical calendar officially used in Saudi Arabia for civil purposes, whereas local moon-sighting depends on the physical observation of the new crescent moon (Hilal) in each specific country. Therefore, calculated dates may sometimes differ by a day from strictly observed local dates.