🕌 Islamic
Understanding the Hijri Calendar and Converting Dates
The Hijri (Islamic) calendar is lunar, so its dates shift about 11 days earlier each year against the Gregorian calendar. Learn how it works, why the dates move, and how to convert between the two.
Updated 20 August 2026 · 2 min read
The Hijri calendar is the calendar of the Islamic world, used to date religious observances from Ramadan to Hajj. If you've ever wondered why Ramadan seems to arrive earlier each year, the answer is in how the calendar is built — it follows the moon, not the sun.
A lunar calendar, not a solar one
The Gregorian calendar most of the world uses for business is solar — its year tracks the Earth's orbit around the sun, at about 365.25 days. The Hijri calendar is lunar: each month follows a cycle of the moon, and twelve of those months make a year of about 354 days.
That drift is why Islamic months move through the seasons over time. Ramadan can fall in summer for a stretch of years, then gradually shift into spring, winter and autumn across roughly a 33-year cycle before returning.
The months and the count from year one
The Hijri calendar has twelve months — Muharram, Safar, Rabi' al-Awwal, Rabi' al-Thani, Jumada al-Awwal, Jumada al-Thani, Rajab, Sha'ban, Ramadan, Shawwal, Dhu al-Qi'dah and Dhu al-Hijjah — alternating roughly between 29 and 30 days. Year one (1 AH) begins with the Hijrah, the Prophet Muhammad's migration from Mecca to Medina in 622 CE, which is where the abbreviation AH (Anno Hegirae, "in the year of the Hijrah") comes from.
Why converting isn't just subtraction
Because the two calendars have different year lengths and different month lengths, you can't convert a date by adding or subtracting a fixed number. The gap between them changes constantly. On top of that, some months' start depends on the actual sighting of the new moon, so a printed calculated date can differ by a day from the observed one in a given country.
That's why a converter is the practical way to move between the two. The Hijri date converter turns any Gregorian date into its Islamic equivalent and back, handling the different month and year lengths for you.
Everyday uses for the conversion
- Finding your zakat date — many people fix their annual zakat on a Hijri date and need to know when it falls this year.
- Planning around Ramadan and Eid, which are set by the Islamic calendar but scheduled into Gregorian diaries.
- Recording an Islamic birthday or anniversary and seeing which Gregorian date it lands on.
Whether you're planning ahead or looking back, converting between the calendars takes the guesswork out of dates that matter. Enter a date below to see its equivalent.
Frequently asked questions
- Why does the Islamic calendar change each year against the Gregorian one?
- Because it's lunar. A Hijri year of twelve lunar months is about 354 days, roughly 11 days shorter than a Gregorian solar year, so Islamic dates fall about 11 days earlier each Gregorian year and move through the seasons over a cycle of around 33 years.
- What does AH mean in a Hijri date?
- AH stands for Anno Hegirae, 'in the year of the Hijrah'. Year 1 AH marks the Prophet Muhammad's migration from Mecca to Medina in 622 CE, which is the starting point the Islamic calendar counts from.
- Can a converted Hijri date be a day off?
- Sometimes. Calculated conversions use astronomical averages, but the start of some Islamic months traditionally depends on the physical sighting of the new moon, which can differ by a day between countries. Treat a converted date as accurate to within about a day for moon-sighting-based months.