How Does the Hijri Calendar Work — and Why Do Its Dates Move Every Year?
If you've ever noticed that Ramadan seems to land at a different time each year — summer one decade, winter the next — you've seen the Hijri calendar in action. Understanding it takes about five minutes, and it makes everything about Saudi scheduling click into place.
The basics
The Hijri (Islamic) calendar is purely lunar. Its structure:
- 12 months, each beginning with the new lunar cycle
- Months run 29 or 30 days, since a lunar cycle is a bit over 29.5 days
- A full year comes to roughly 354 days — about 11 days shorter than the Gregorian solar year
That 11-day gap is the whole story of the "moving dates." Because the Hijri year is shorter, every Hijri month arrives about 11 days earlier on the Gregorian calendar each year. Ramadan, the month of Dhu al-Hijjah (when Hajj takes place), and every other Islamic observance cycle backward through the Gregorian seasons, completing a full loop roughly every 33 years.
Bottom line: lunar months are shorter than solar ones, so Hijri dates drift earlier every Gregorian year.
The months
The twelve Hijri months, in order: Muharram, Safar, Rabi' al-Awwal, Rabi' al-Thani, Jumada al-Awwal, Jumada al-Thani, Rajab, Sha'ban, Ramadan, Shawwal, Dhu al-Qa'dah, Dhu al-Hijjah. The ones a traveler most needs to recognize are Ramadan (the fasting month), Shawwal (which opens with the Eid al-Fitr holiday), and Dhu al-Hijjah (the Hajj month, containing Eid al-Adha).
What "Umm al-Qura" means
Saudi Arabia doesn't leave civil dates to ad-hoc moon watching. The Kingdom publishes an official computed calendar — the Umm al-Qura calendar, maintained by the authority at ummulqura.org.sa — which fixes the civil Hijri date for government, business, and administrative use, and serves as the standard reference for date conversion.
Two things are worth keeping straight:
- Civil dates follow the published Umm al-Qura calendar and are known well in advance
- Religious observances — the actual start of Ramadan, the two Eids — are confirmed by official moon sighting announcements, which occasionally differ from the pre-computed date by a day
This is why your Saudi colleagues may say Eid is "expected" on a given date rather than scheduled: the final call comes with the sighting.
Bottom line: the Umm al-Qura calendar sets the official civil date; moon sightings confirm the religious ones.
Why this matters for planning
For anyone dealing with Saudi Arabia from the US, the practical takeaways:
- Convert your dates. A trip planned on Gregorian dates alone can land you in Ramadan or Hajj season without realizing it — periods when crowds, prices, and daily rhythms change dramatically. The official calendar site is the standard conversion reference.
- Expect year signatures like 1448 AH. Hijri years count from the Hijra (622 CE); "AH" is the era marker you'll see on Saudi documents alongside the Gregorian date.
- Hajj season affects Umrah logistics. The Ministry of Hajj and Umrah regulates pilgrimage timing, and Umrah access is restricted around the Hajj period each year — another date that moves with the lunar calendar.
Bottom line: check the Hijri calendar before you commit to travel dates. It takes two minutes and prevents the most common first-timer scheduling surprise. Then run your plans through the Umrah planning checklist to see what else is left.