Hijri vs Gregorian Calendar: The Key Differences
Most of the world uses the Gregorian calendar for civil life, while Muslims use the Hijri calendar for worship. Here are the differences that matter in practice.
Sun or moon
The Gregorian calendar is solar: its year follows the Earth's orbit around the sun, so its months stay in the same season. The Hijri calendar is lunar: each month follows one cycle of the moon's phases, with no link to the seasons.
Length of the year
| Hijri | Gregorian | |
|---|---|---|
| Months | 12 lunar months | 12 months |
| Days in a month | 29 or 30 | 28 to 31 |
| Days in a year | 354 or 355 | 365 or 366 |
| Year 1 | 622 CE (the Hijra) | Traditional year of the birth of Jesus |
| Day begins | At sunset | At midnight |
| Abbreviation | AH | CE / AD |
The year numbers drift
Because the Hijri year is about 11 days shorter, it gains roughly one year on the Gregorian calendar every 33 years. That is why you cannot just subtract 622 from a Gregorian year. A good approximation is:
- Hijri year ≈ (Gregorian year − 622) × 33 ÷ 32
- Gregorian year ≈ Hijri year × 32 ÷ 33 + 622
For an exact date, use the Hijri date converter.
Leap years
The Gregorian calendar adds 29 February in leap years to stay in step with the sun. Calculated Hijri calendars add a 30th day to Dhu al-Hijjah in some years, making a 355-day year; in the tabular Islamic calendar this happens in 11 years of every 30. In a sighting-based calendar there are no fixed leap years: each month simply has 29 or 30 days depending on the crescent.
Why both matter
Islamic occasions such as Ramadan, Hajj and the two Eids are tied to Hijri dates, but daily life runs on the Gregorian calendar. Knowing both, and how they shift against each other, is the reason a site like HijriTime exists. Browse a full year in the Hijri calendar, which shows each Hijri day with its Gregorian date.
Sources and Verification
This article was written by Fatah Nasrat and checked against the official, scientific and academic sources below. HijriTime does not copy source texts; it explains their methods and findings in its own words.
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