What's the difference between the Hijri and Gregorian calendars?
The Hijri calendar is a lunar calendar based on the moon's cycle around the Earth, with a year made up of 12 lunar months of 29 or 30 days each — making the Hijri year about 11 days shorter than the Gregorian year. The Gregorian calendar, by contrast, is a solar calendar based on the Earth's orbit around the sun. Because of this gap, the start of each Hijri month gradually shifts through the Gregorian seasons over the years.
Why does the Hijri calendar start from the Prophet's migration?
The Hijri calendar was adopted during the caliphate of Umar ibn al-Khattab, and the migration (Hijra) of the Prophet Muhammad ﷺ from Mecca to Medina was chosen as the starting point of the Islamic era, given the pivotal role this event played in establishing the first Islamic state.
Occasions where you need the Hijri date
- Fasting and holidays: Ramadan, Eid al-Fitr, Eid al-Adha, and the days of Tashreeq.
- Hajj and Umrah: for determining ritual dates and the Hajj season.
- Zakat calculation: since the Zakat year (Hawl) is measured in lunar, not solar, years.
- Contracts and inheritance: some official and religious documents are dated using the Hijri calendar in several Arab countries.
Frequently Asked Questions
Is this conversion exactly the same as the official Umm al-Qura calendar?
Usually yes, but it may differ by one day in some months, since the official Umm al-Qura calendar is based on officially adopted astronomical calculations that are sometimes adjusted by administrative decisions, while this tool uses the standard astronomical calculation for the Hijri calendar.
How many days are in a Hijri year compared to a Gregorian year?
A lunar Hijri year has 354 or 355 days, while a Gregorian year has 365 or 366 days (in a leap year) — a difference of about 10 to 11 days each year.
Why does Ramadan shift every year on the Gregorian calendar?
Because the Hijri year is about 11 days shorter than the Gregorian year, Ramadan (and every other Hijri month) moves about 11 days earlier each Gregorian year, cycling through all the seasons over roughly 33 Gregorian years.