Hijri vs Gregorian Calendar
Two of the world's most widely used calendar systems sit side by side. Here is how they differ — and why both matter in Singapore.
Quick comparison
- Hijri: purely lunar, ~354 days per year, 12 months of 29 or 30 days.
- Gregorian: solar, 365 or 366 days, 12 months of 28 to 31 days.
- Hijri year is about 11 days shorter, so Hijri dates drift earlier through the Gregorian seasons each year.
- Hijri epoch: 622 CE (the Hijrah). Gregorian epoch: 1 CE (introduced 1582 CE, reform of the Julian calendar).
Year length and leap years
The Gregorian calendar adds a leap day on 29 February once every four years (with century exceptions), keeping the year aligned with Earth's orbit around the sun.
The observational Hijri calendar has no leap days — month length depends on moon sighting. The tabular Hijri variants (such as Umm al-Qura's published civil calendar) use a 30-year cycle in which 11 years are 355 days long and 19 years are 354 days long.
How months begin
- Gregorian: months begin on fixed dates regardless of astronomy.
- Hijri: months begin at the first sighting of the new crescent moon after sunset on the 29th. If not sighted, the month rolls over to 30 days.
When each is used
In Singapore, the Gregorian calendar governs civil life — work, school, government, and banking. The Hijri calendar governs religious observance for Muslims: Ramadan, the two Hari Raya, Maulidur Rasul, Isra' Mi'raj, Awal Muharram, and Hajj. Both calendars appear together on the MUIS annual takwim and on this site's live converter.
Converting between the two
The arithmetic is non-trivial because the relationship is not constant: a Hijri month may be 29 or 30 days depending on sighting, and the start of the Hijri year drifts earlier each Gregorian year. Use the Hijri Date Converter on the home page to translate any date instantly under MUIS, MABIMS or Umm al-Qura rules.
Common questions
Why do Ramadan and Hari Raya happen at different times each year?
Because the Hijri year is 11 days shorter than the Gregorian year. Over roughly 33 years, every Hijri date cycles through all four Gregorian seasons.
Why do different countries sometimes start Ramadan on different days?
Because some authorities follow local moon sighting, others follow regional coordination (such as MABIMS in Southeast Asia), and others rely on astronomical calculation (such as Saudi Arabia's Umm al-Qura). Geography also matters — the crescent may be visible in one country but not another on the same evening.
Is the Hijri calendar the same as the Arabic calendar?
Yes — Hijri, Islamic, and Arabic calendar are common names for the same lunar system used across the Muslim world.