Topic
Hijri Dates and the Saudi Calendar
Three tools built around a single awkwardness — the Hijri calendar is lunar, the calendar your bank and your phone use is solar, and they drift against each other every year. This explains what Umm al-Qura is, why the dates move, and why the zakat calculator belongs on this page rather than with the other finance tools.
Reviewed 3 September 2026
What Umm al-Qura is
Umm al-Qura is the civil calendar of Saudi Arabia — the one on government paperwork, employment contracts, iqama expiry dates and school terms. It is calculated in advance from astronomical criteria rather than declared by observation, which is what makes conversion possible at all: a converter can only work from a calendar that is decided ahead of time.
That is also why a converted date and an announced date can differ by a day. Religious observances — the start of Ramadan, the day of Eid — are declared on sighting, and sighting can fall on either side of the calculated date. Neither is wrong; they are answering different questions. For anything administrative, the calculated date is the one your paperwork uses. For anything religious, wait for the announcement.
Why the dates keep moving
A lunar year of twelve months runs about 354 days against the solar year's 365. The gap is close to eleven days, and it is not corrected — there is no leap month. So every Hijri date arrives roughly eleven days earlier in the Gregorian year than it did last time, and works its way back through the seasons over about thirty-three years.
The practical consequence is that nothing anchored to a Hijri date can be scheduled by taking last year's Gregorian date and adding a year. A contract that renews on a Hijri date, a lease, an annual religious obligation — each one needs converting again.
Why zakat is on this page
Zakat is due after a hawl — a full lunar year during which the wealth has been held. Not a calendar year, and not the year your accounting software uses.
So the date it falls due moves earlier by about eleven days each Gregorian year, exactly like every other Hijri date, and working out when it is due is a conversion problem before it is an arithmetic one. That is the link between these two tools, and it is not obvious from either of them alone. The timezone tool is here for the third version of the same friction: working across the Gulf and somewhere else means two calendars and two working weeks.
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Common questions
Which calendar does the converter use?
Umm al-Qura, the Saudi civil calendar. That is the one to check against a residence permit, a contract or an official form. It is calculated rather than observed, so it can differ by a day from a sighting-based announcement — which is a real difference, not an error in either.
Hijri Converter →Why does my date differ by one day from another site?
Almost always because the other site is using a tabular Hijri calendar — a simple arithmetic rule — rather than Umm al-Qura. The two agree most of the time and differ by a day fairly often, and the direction of the disagreement reverses, so there is no fixed offset you can apply to fix it.
How Hijri conversion works →Can I plan next year's dates from this year's?
Not by adding a year. Hijri dates fall about eleven days earlier in the Gregorian calendar each year, with no leap month to correct it, so anything anchored to a Hijri date has to be converted again each time.