Gregorian → Umm al-Qura
Upcoming Islamic Dates
How the Umm al-Qura Date Conversion Works
Why You Need a Hijri-Gregorian Converter
Muslims worldwide need to convert between the Islamic Hijri calendar and the Gregorian calendar for planning religious observances, travel, and administrative tasks. The Umm al-Qura calendar — Saudi Arabia’s official civil Hijri calendar — is the most widely used reference for Hijri dates because it provides dates calculated years in advance using astronomical data from KACST.
The Bridge: Julian Day Number (JDN)
Different calendars have unique starting points and month-length rules. To convert accurately between them, a neutral reference system called the Julian Day Number (JDN) is used. The JDN is a continuous count of days since January 1, 4713 BC, providing a universal “day counter” that both calendars can connect to.
Step-by-Step Conversion Process
- Gregorian → JDN: The Gregorian date you enter is first converted into its unique Julian Day Number using a standard astronomical formula.
- JDN → Umm al-Qura: The JDN is then matched against the official Umm al-Qura month-start tables to find the exact Hijri day, month, and year.
- Weekday calculation: The day of the week is derived from the JDN (JDN mod 7), giving you the Arabic weekday name alongside the result.
Reversing the Process
Converting from an Umm al-Qura date to a Gregorian date uses the same logic in reverse. The Umm al-Qura month-start table gives us the JDN of the first day of the selected Hijri month. Adding the day offset produces the exact JDN, which is then converted back into the Gregorian calendar format.
Accuracy and Range
This converter is accurate for dates between 1356 AH (14 March 1937 CE) and 1500 AH (16 November 2076 CE). Outside this range, the official Umm al-Qura tables are not published, so conversions may be less reliable. For dates within this range, the results match the official KACST publication exactly.
Frequently Asked Questions
How do I convert Gregorian dates to Hijri dates?
Select the Gregorian day, month, and year from the dropdowns above and click Convert Date. The tool instantly returns the corresponding Hijri date according to the official Umm al-Qura calendar used in Saudi Arabia.
How accurate is the Umm al-Qura date conversion?
The conversion uses the official Umm al-Qura calendar tables published by KACST (King Abdulaziz City for Science and Technology). These are the same tables used by the Saudi Arabian government for civil and administrative purposes. Dates are accurate for the range 1356 AH to 1500 AH.
Why might the converted date differ from my local Islamic date?
The Umm al-Qura calendar uses astronomical calculations based on Mecca’s coordinates. Countries that rely on local moon sighting — such as Pakistan, India, or Bangladesh — may observe months starting one day earlier or later than the calculated Saudi date.
What is the Julian Day Number used in date conversion?
The Julian Day Number (JDN) is a continuous count of days since January 1, 4713 BC. It serves as a universal bridge between calendar systems. Both Gregorian and Hijri dates are first converted to JDN, then from JDN to the target calendar, ensuring mathematical accuracy.