Calculated tabular calendar
Islamic Calendar and Hijri Date Converter
Convert Gregorian and calculated Hijri dates or browse a tabular Hijri month. Results are mathematical estimates and may differ from regional observations or official announcements.
Selected dates, month, week-start choice, and adjustment remain only in this page’s memory and clear on refresh or Reset.
Values are not added to the URL, stored as calendar preferences, or sent to an external Hijri provider. No location is used.
What this tool does
Converts between Gregorian and Hijri dates and displays a Hijri month grid, using the tabular civil calendar — an arithmetic scheme, not an observation of the moon.
When to use it
- You need a Hijri date for a record, a planning document, or a Zakat valuation date.
- You want to see roughly where a Hijri month falls in the Gregorian year in order to plan ahead.
- You are working out how far apart two dates are in lunar rather than solar terms.
How the figure is produced
- Dates are converted through the Julian Day Number, using the standard Hijri epoch of JDN 1,948,440.
- Month lengths follow the tabular civil scheme, in which months alternate 30 and 29 days and a leap day is added to the final month in designated years of a 30-year cycle.
- Every conversion is verified by converting the result back and checking it matches; if it does not, the tool reports the date as unavailable rather than showing a figure it cannot stand behind.
- A manual adjustment of up to two days in either direction is available, so a calculated date can be aligned with a local announcement without the underlying arithmetic being altered.
Worked example
Someone needs the Hijri equivalent of a Zakat valuation date so that the following year's review falls on the same lunar date.
- Method
- Tabular civil (arithmetic)
- Epoch used
- Julian Day Number 1,948,440
- Month lengths
- Alternating 30 and 29 days
- Leap day
- Added to Dhu al-Hijjah in designated years
- Manual adjustment available
- −2 to +2 days
- Round-trip verification
- Applied to every conversion
Because a lunar year is roughly eleven days shorter than a solar one, a Zakat date fixed in Hijri terms moves earlier through the Gregorian year each cycle. Fixing the date in one calendar and reading it in the other is the point of this converter.
Assumptions built in
- The tabular civil calendar is a fixed arithmetic rule. It does not model the actual visibility of the crescent moon from any particular place.
- Conversion is supported for Gregorian years 1900–2100 and Hijri years 1317–1524. Dates outside that window are refused rather than extrapolated.
- Dates are treated as whole calendar days; no time zone or sunset boundary is applied, although a Hijri day conventionally begins at sunset.
Limitations
- A calculated date can differ from the observed date by a day or more, and the direction of the difference varies by region. This is normal for a tabular calendar, not a defect.
- Nothing here is an official announcement. Ramadan, Eid, and Dhu al-Hijjah dates are declared by the relevant authority for your location, and the calculated date does not override that declaration.
- The tool makes no moon-sighting prediction and does not tell you when a crescent will be visible.
- For religiously significant dates, confirm with your local authority before acting on anything shown here.
How this differs from the related tools
- Islamic Events
Lists the significant dates in the year with the same calculated-versus-observed caveat, rather than converting an arbitrary date you supply.
- Ramadan Hub
Covers Ramadan planning specifically, including why the start date is announced rather than calculated.
- How to calculate Zakat
Explains why the Hijri date matters for Zakat — Hawl is a lunar year, so a Gregorian anniversary drifts against it.