What Is the Hijri Calendar? A Simple Guide to the Islamic Lunar Calendar

Prayer Times blog ยท September 2026 ยท 6 min read

Every year, Ramadan arrives about eleven days earlier than the year before. Eid hops around the seasons. And the Islamic year number โ€” currently in the 1440s โ€” is nearly 600 years "behind" the Gregorian one. None of this is a mistake. It's what happens when you run a civilization's calendar on the moon instead of the sun.

A year measured in moons

The Hijri calendar is lunar: each month begins with the sighting of the new crescent moon, and lasts 29 or 30 days. Twelve such months make a year of about 354 days โ€” roughly 11 days shorter than the solar Gregorian year.

That 11-day gap is the whole story behind the "moving Ramadan." Because the Hijri year is shorter, every Islamic date drifts backward through the seasons, completing a full cycle roughly every 33 years. Anyone who has fasted Ramadan in both blazing July and chilly January has lived this cycle personally. There's a quiet beauty in it: over a lifetime, every Muslim experiences Ramadan in every season.

The 12 months

1. MuharramSacred month; the Islamic New Year
2. Safar
3. Rabi' al-AwwalBirth month of the Prophet ๏ทบ
4. Rabi' al-Thani
5. Jumada al-Ula
6. Jumada al-Akhirah
7. RajabSacred month
8. Sha'banThe month before Ramadan
9. RamadanThe month of fasting
10. ShawwalEid al-Fitr falls on the 1st
11. Dhu al-Qa'dahSacred month
12. Dhu al-HijjahHajj and Eid al-Adha; sacred month

Four months are traditionally sacred โ€” Muharram, Rajab, Dhu al-Qa'dah and Dhu al-Hijjah โ€” a pre-Islamic Arabian custom of truce months that Islam retained.

Where "Hijri" comes from

The calendar counts from the Hijrah โ€” the Prophet Muhammad's ๏ทบ migration from Mecca to Medina in 622 CE โ€” which is why it's called "Hijri" and abbreviated AH (Anno Hegirae, "in the year of the Hijrah"). The second caliph, Umar ibn al-Khattab, formalized it around 638 CE when the growing Muslim state needed consistent dating for records and correspondence. They chose the Hijrah as year 1 not because nothing important happened before it, but because it marked the birth of the Muslim community as an organized society.

So when you see "1447 AH," it means 1,447 lunar years since that migration. The ~579-year gap with the Gregorian count comes from two things: the later start date (622 CE) and the shorter lunar year accumulating over fourteen centuries.

Moon sighting vs. calculation

Here's a nuance that causes real-world confusion: traditionally, a new month begins when the crescent is physically sighted โ€” which depends on weather, geography, and human eyes. That's why Ramadan or Eid sometimes starts on different days in different countries. Many communities now use astronomical calculation instead, which is precise and predictable.

Our Prayer Times page shows the Hijri date computed astronomically โ€” accurate for planning, though your local community's announced date (based on sighting) is what to follow for fasting and Eid. When they differ by a day, that's normal and expected, not an error.

Why no leap months? Some lunar calendars (like the Hebrew and Chinese ones) insert an extra month every few years to stay aligned with the seasons. The Hijri calendar deliberately doesn't โ€” the Quran (9:36-37) fixes the year at twelve months. The drift through the seasons isn't a bug; it's the design.

Why it still matters

The Hijri calendar isn't a historical curiosity โ€” it sets the rhythm of Muslim life: when to fast, when to perform Hajj, when the Eids fall, even the recommended fasting days scattered through the year. Living by two calendars at once โ€” Gregorian for work and school, Hijri for worship โ€” is second nature to Muslims worldwide. The moon that marked time for desert caravans fourteen centuries ago still marks it today. You just have to look up.