The Hijri Calendar Explained: Months, Moon Sighting and Umm al-Qura
The Hijri (Islamic) calendar is a lunar calendar used to date religious events such as Ramadan, Hajj and the two Eids. It is the calendar behind the Hijri dates that appear on our timetables.
Counting from the Hijra
Year 1 of the calendar marks the Prophet's migration (Hijra) from Makkah to Madinah in 622 CE. Years are written with "AH", short for the Latin anno Hegirae, "in the year of the Hijra". In November 2026 the Hijri year is 1448.
Twelve lunar months
- Muharram
- Safar
- Rabi' al-Awwal
- Rabi' al-Thani
- Jumada al-Awwal
- Jumada al-Thani
- Rajab
- Sha'ban
- Ramadan
- Shawwal
- Dhu al-Qi'dah
- Dhu al-Hijjah
Each month begins with the new crescent moon and lasts 29 or 30 days, the time the moon takes to go through its phases (about 29.5 days). Twelve months add up to 354 or 355 days, which is about 10 or 11 days shorter than a solar year.
Why Ramadan moves through the seasons
Because the lunar year is shorter than the solar year, Hijri months start about 10 to 11 days earlier on the Gregorian calendar each year. Ramadan therefore travels through all seasons over a cycle of about 33 years. Fasting hours are long in summer and short in winter, and over a lifetime a Muslim experiences both.
When does the day begin?
In the Islamic reckoning each day begins at sunset (Maghrib), not at midnight. The night of a date comes before its day. For example, the night before Friday is "Friday night" (laylat al-Jumu'ah). Most digital calendars change the date at midnight, so there is an overlap of a few hours between conventions.
Moon sighting or calculation?
Two approaches are used to decide the start of a month:
- Sighting: Following the teaching to fast and break the fast on seeing the crescent, many countries and communities rely on actual or reported sightings after the 29th day, and complete 30 days when the sky is cloudy.
- Calculation: Other authorities rely on astronomical calculations, either to confirm sighting or to set dates in advance. Saudi Arabia's Umm al-Qura calendar is calculation-based, using criteria tied to the moon's position at Makkah, and is widely used for civil dates. Many software libraries and phones implement it.
Why dates can differ by a day
The new crescent is visible at different times in different places. Where it is sighted, or what criteria are accepted, can differ, so one country may start Ramadan or Eid a day before or after another. Both follow valid, recognised processes. That is why the Hijri date on our timetables, which is calculated, may not match your country's official date for a month's start. For religious observances, follow your local announcement.
Using the calendar
Our monthly timetables show the Hijri date next to each Gregorian date, so you can follow the Islamic date through the month. See also our guide to Ramadan timings.