Hijri to Gregorian converter — historical dates

Tool notes & guidance

How to use this tool

1. Enter the day, named Hijri month and year shown on your document. AH means the lunar Hijri era; do not enter a Solar Hijri year.
2. Leave adjustment at zero unless another source establishes a difference. The converter checks the date against tabular month lengths.
3. Read the Gregorian and Julian dates, then compare the month table and your original source. Record the calendar and any adjustment with your citation.

How historical Hijri date conversion works

A reverse Islamic date lookup

Enter a Hijri date to find its calculated Gregorian equivalent. The tool also gives the corresponding Julian date and a complete table for the Hijri month. This is useful for family records, manuscript dates, inscriptions and chronological research when the source uses lunar AH years.

The tabular method

The converter uses a civil Friday epoch: 1 Muharram AH 1 corresponds to 16 July 622 in the Julian calendar. Odd-numbered months have 30 days and even-numbered months have 29; Dhu al-Hijjah has 30 in leap years. The leap years within each 30-year cycle are 2, 5, 7, 10, 13, 16, 18, 21, 24, 26 and 29. Other tabular variants exist, so always state this convention.

Gregorian and Julian results

Gregorian output uses the proleptic Gregorian calendar: its rules are extended backwards before the calendar was introduced. Julian output uses Julian rules throughout. We do not assume that every country switched calendars in October 1582. Choose the version appropriate to the document and place; an older European record may use Julian dates long after 1582.

Historical accuracy and moon sighting

A tabular conversion is a reproducible calculation, not proof of which date a community observed. Crescent sightings, regional practice, transcription errors and different tabular epochs can change a comparison. The adjustment field shifts the calculated result by the number of days you select; it does not model actual crescent visibility. The displayed date denotes the civil daytime date. An Islamic day begins at sunset on the preceding civil date.

Worked historical example

With the default convention, 1 Muharram AH 1 gives 19 July 622 in the proleptic Gregorian calendar and 16 July 622 in the Julian calendar. The three-day difference is a calendar difference, not a moon-sighting adjustment. As a modern arithmetic example, 1 Muharram AH 1445 gives 19 July 2023 Gregorian with no adjustment.

What to record for genealogy and manuscripts

Keep the exact wording, month spelling, year and location of the original source. Distinguish AH from CE/AD and from Solar Hijri dates. If the source names a weekday, use it as a cross-check rather than changing the input until it matches. For an unknown day, use the full-month table to report a date range instead of inventing a precise birthday or event date.

Hijri to Gregorian or Gregorian to Hijri?

This page starts with the Hijri day, month and year and supports historical lookup. For the opposite direction, use the Gregorian-to-Hijri date converter, which uses your browser’s Umm al-Qura implementation. Its calendar differs from this tabular calculation; the tools are not guaranteed to give inverse results. See our calculation methods for the wider tool collection.

Common questions

Sources & review status

• U.S. Naval Observatory: Islamic calendar and epoch
• NASA: calendars and their history

Read the calculation method and limits and editorial standards and review status. These educational tools have not been independently certified by a scholar.