Why does my date differ from the official calendar by a day?

The official Islamic calendar in many countries follows the visible crescent moon, while this tool uses the tabular algorithm. A ±1-day difference is normal and expected.

Which tabular variant is this?

The Kuwaiti algorithm — a 30-year cycle with 11 leap years and the standard alternating 30/29-day month pattern. It is the variant used by Microsoft, ICU, and most Linux distributions for the Hijri locale.

Does it work for years before AH 1?

No. The tool only accepts AH years 1–9999. The Hijri calendar begins at AH 1, Muharram 1 (Friday, 16 July 622 CE Julian).

How does it handle leap years?

In leap years, Dhu al-Hijjah (month 12) has 30 days instead of 29. The leap-year pattern is the standard Kuwaiti set listed above.

Islamic Calendar Converter

Convert between Gregorian and tabular Hijri dates (Kuwaiti algorithm).

Written by Golam Rabbani, Founder & Lead Engineer

This interactive tool requires JavaScript. Read the formula and worked example below; you can compute the result by hand.

How to use this islamic calendar converter

Pick the direction: Gregorian → Hijri, or Hijri → Gregorian.
Enter the Gregorian date, or enter the Hijri year, month, and day.
Press "Convert".
Read the formatted result with month names and numeric components.
Use Copy to share the converted date or Reset to clear.

About this islamic calendar converter

This tool converts between the Gregorian calendar and the Islamic (Hijri) calendar using the <strong>tabular Islamic calendar</strong> — the Kuwaiti algorithm. Tabular conversion uses a fixed 30-year cycle with 11 leap years (years 2, 5, 7, 10, 13, 16, 18, 21, 24, 26, and 29) and alternating 30/29-day months. It is the algorithm used by most software, government records, and computer systems because it is exact, reversible, and independent of moon sighting.

Because real Islamic observance starts each month from the visible new crescent moon, the actual lunar date in any given country can differ by ±1 day from the tabular date. The tool states this in the UI so you can pick the answer that matches your need: tabular for documents and software, observational for religious observance.

Worked example: convert 2026-05-28 (Gregorian) to Hijri. The tool reports 11 Dhu al-Qa‘dah 1447 AH. Convert 1 Ramadan 1447 AH back to Gregorian and it gives 1447-01-19 Ramadan = roughly mid-February 2026. The numeric breakdown alongside the formatted answer makes it easy to plug into other systems.

Useful for converting birthdays, contract dates, anniversaries, or any document that needs both calendar systems on it. For religious dates such as the start of Ramadan or Eid, defer to your local moonsighting authority.

FAQ

Why does my date differ from the official calendar by a day?: The official Islamic calendar in many countries follows the visible crescent moon, while this tool uses the tabular algorithm. A ±1-day difference is normal and expected.
Which tabular variant is this?: The Kuwaiti algorithm — a 30-year cycle with 11 leap years and the standard alternating 30/29-day month pattern. It is the variant used by Microsoft, ICU, and most Linux distributions for the Hijri locale.
Does it work for years before AH 1?: No. The tool only accepts AH years 1–9999. The Hijri calendar begins at AH 1, Muharram 1 (Friday, 16 July 622 CE Julian).
How does it handle leap years?: In leap years, Dhu al-Hijjah (month 12) has 30 days instead of 29. The leap-year pattern is the standard Kuwaiti set listed above.