What is the Hijri to Gregorian Date Converter?
This tool converts a date in the Hijri (Islamic lunar) calendar into its corresponding date in the Gregorian (Western) calendar. It uses the arithmetic, or tabular, Islamic calendar rather than an astronomical crescent-sighting calendar, so a computed date may differ by plus or minus one day from a religiously observed date. The Hijri calendar is a pure lunar calendar of 12 months totalling 354 days in a common year and 355 days in a leap year. An Islamic day begins at sunset of the preceding Gregorian day, so the Gregorian date shown corresponds to the daytime portion. This conversion is universal and not tied to any country.
How to use it
Pick a calendar type (Standard, Kuwaiti, or Fatimid), each of which uses a slightly different set of leap years within the 30-year cycle. Choose the starting Hijri month and enter the Hijri year in AH. Then select how long a period to convert: one month, two months, half a year, or a full year. The result shows the Gregorian start date (day 1 of the chosen month), the Gregorian end date (last day of the final month), the total number of days, and a month-by-month table.
The formula
The Hijri date is first converted to a Julian Day Number (JDN): $$\text{JDN} = \text{day} + \left\lceil 29.5 \times (\text{month} - 1) \right\rceil + (\text{year} - 1) \times 354 + \text{leapDaysBefore}(\text{year}) + \text{EPOCH} - 1,$$ with \(\text{EPOCH} = 1948440\). The JDN is then mapped to a Gregorian date with the Fliegel-Van Flandern algorithm. Each 30-year cycle contains 11 leap years, giving 10631 days per cycle.
Worked example
Convert 1 Ramadan 1447 AH (Standard). \(\left\lceil 29.5 \times 8 \right\rceil = 236\); \(1446 \times 354 = 511884\); leap days before \(= 530\); $$\text{JDN} = 1 + 236 + 511884 + 530 + 1948440 - 1 = 2461090,$$ which is 18 February 2026. Ramadan has 30 days, so the period ends 19 March 2026.
FAQ
Why might the date be off by a day? The tabular calendar is purely arithmetic; clerics who confirm a new month by post-sunset crescent observation can report a date one day earlier or later.
Which calendar type should I choose? Standard (Tabular type II) is the most common; Kuwaiti matches the Microsoft algorithm; Fatimid follows the Ismaili Bohra rule.
Can I convert years before 1 AH? No - the converter requires a positive Hijri year, since earlier years extrapolate before the calendar epoch.
