# The Hijri Calendar, and Why Dates Move

The Islamic year is lunar and about eleven days shorter than the Gregorian one, which is why Ramadan arrives earlier each year.

## Why does Ramadan move earlier every year?

Because the Hijri calendar follows the moon. Twelve lunar months come to about 354 days, roughly eleven days fewer than the 365 of a solar year. Since the Hijri calendar makes no adjustment to stay aligned with the seasons, every Islamic date shifts about eleven days earlier in the Gregorian calendar each year, and works its way through all four seasons over about 33 years.

## The twelve months

Muharram, Safar, Rabi' al-Awwal, Rabi' al-Thani, Jumada al-Ula, Jumada al-Akhirah, Rajab, Sha'ban, Ramadan, Shawwal, Dhu al-Qi'dah and Dhu al-Hijjah. Each is 29 or 30 days, following the lunar cycle of about 29.5 days. The year counts from the migration to Madinah in 622 CE, which is what AH — anno Hegirae — refers to.

## Calculated dates against sighted dates

A tabular Hijri date is arithmetic: it assumes months alternate in a fixed pattern, and can be computed years ahead. An announced date follows an actual sighting of the new crescent, which depends on weather, location and the criteria a given authority applies. The two commonly differ by a day. Dates on this site are tabular, and say so.

## Why authorities announce different days

The crescent is visible from some parts of the world before others on the same evening, and authorities differ on whether a sighting elsewhere counts locally. This is why Eid can fall on different days in different countries, and sometimes within one country.

## Common questions

**How many days is a Hijri year?**

354 or 355, against 365 or 366 in the Gregorian calendar.

**Can I know the exact date of Ramadan years ahead?**

You can compute the tabular date exactly, but the observed start depends on a sighting and may differ by a day.

**What does AH mean?**

Anno Hegirae — the year of the migration. 1448 AH means the 1448th year since 622 CE.

## See this on the site

- [The Hijri calendar with Gregorian dates](https://quranonlineread.com/calendar/)
- [1448 AH month by month](https://quranonlineread.com/calendar/1448/)
- [When Ramadan falls](https://quranonlineread.com/calendar/events/ramadan/)
- [When Eid al-Fitr falls](https://quranonlineread.com/calendar/events/eid-al-fitr/)

## Related

- [How Prayer Times Are Calculated](https://quranonlineread.com/learn/how-prayer-times-are-calculated/)

## Source

Published by: QuranOnline
Canonical page: https://quranonlineread.com/learn/the-hijri-calendar/
Last updated: 2026-09-08T17:04:00.171Z
Editorial policy: https://quranonlineread.com/about/#editorial