How the conversion works
- Hijri (Umm al-Qura): Saudi Arabia’s official calendar, worked out from fixed astronomical rules, so any date can be known in advance. It covers 1300 to 1600 AH.
- Tabular Hijri: an arithmetic calendar on a fixed 30-year cycle. Many programs use it, and it can run a day ahead of or behind Umm al-Qura.
- Julian: Julius Caesar’s calendar, with a leap year every four years without exception. It has drifted until it is 13 days behind the Gregorian between 1900 and 2100, and some Orthodox churches still date their feasts by it, including Christmas for the Russian and Serbian churches and Easter for Orthodox churches generally.
- Coptic: twelve months of 30 days plus a short month of 5 days, or 6 in a leap year. The Coptic year usually starts on 11 September, or 12 September before a Gregorian leap year.
- Persian and Buddhist: the Persian calendar is solar and starts at the spring equinox. The Buddhist year is the Gregorian year plus 543, used in Thailand.
Where is the Greek calendar?
Greece has used the Gregorian calendar officially since 1923. What people call the “old Greek calendar” is really the Julian calendar that the Orthodox churches follow, so choose “Julian” to see a feast date in the old style. Ancient Greek calendars, such as the Athenian one with its Attic months, are no longer in use and do not map onto today’s dates in a fixed way.
Why the Hijri date differs between sources
A Hijri month starts when the new moon is sighted, and astronomical calculation only estimates it. Saudi Arabia’s Umm al-Qura can run a day ahead of an announcement by Egypt’s Dar al-Ifta, and that is normal. Use the tool for planning and estimates, and confirm the actual date with your country’s official body when worship or a contract depends on it.
Need Hijri dates in your own system? We build Arabic management systems that keep the Hijri date beside the Gregorian one on invoices, contracts and rent schedules.
Questions
How do I convert a Hijri date to Gregorian?
Choose “Hijri (Umm al-Qura)” as the calendar, enter the day, the month number and the Hijri year, and the Gregorian date and weekday appear below. For example 1 Ramadan 1447 AH is 18 February 2026.
How do I convert Gregorian to Hijri?
Leave the calendar on Gregorian and enter the date, then choose “Hijri (Umm al-Qura)” under “I want the date in”. The table lists every other calendar for the same day.
Why is the Hijri date a day off from the calendar I use?
The start of a month follows the moon sighting in your country, while Umm al-Qura and the tabular calendar are fixed calculations. A difference of a day or two is possible, so for religious dates and contracts rely on the official body.
What is the difference between Umm al-Qura and tabular Hijri?
Umm al-Qura is Saudi Arabia’s official calendar, built on astronomical rules. The tabular calendar is a fixed arithmetic cycle of 30 years. They can differ by a day in some months.
What is the Julian calendar and why is it 13 days behind?
Julius Caesar’s calendar, with a leap year every four years. That year is about 11 minutes longer than the solar year, so the difference built up to 13 days in the 20th and 21st centuries. Some Orthodox churches still date feasts by it.
Does Greece use its own calendar?
No. Greece has used the Gregorian calendar officially since 1923. The Julian calendar is still followed by some Orthodox churches for certain feasts.
Do you store the dates I enter?
No. The calculation runs in your browser and the dates are not sent to us.
More free tools
- Garment cost calculator: Work out the cost of one garment from fabric, trims, labour, overheads and rejects, and the selling price for the margin you want. Free, no sign-up.
- Fabric consumption calculator: Work out fabric per piece in metres and kilograms from the marker length and the pieces it holds, plus the plies and fabric needed for a whole order. Free, no sign-up.
- Break-even calculator for a garment factory: Work out how many pieces a month cover your factory’s fixed costs, the output a target profit needs, and your margin of safety at current output. Free, no sign-up.
- Worker output and piece-rate calculator: Work out a worker’s or a line’s daily output from the standard time of a piece, the piece rate that pays a target wage, and actual efficiency from real output. Free, no sign-up.
- VAT calculator: Add VAT to a price or take it out of a VAT-inclusive one, for one item or several, at Egypt’s 14%, Saudi Arabia’s 15%, the UAE’s 5% or any rate you enter. Free, no sign-up.
- Study schedule maker: Enter your subjects, their exam dates and how many study sessions a day you can do, and get a day-by-day study schedule ready to print or save as PDF. Free, no sign-up.
- BMI calculator and healthy weight range: Work out your BMI from height and weight, see your category, the healthy weight range for your height and how far you are from it. Adults 18+. Free.
- Calorie calculator: BMR and daily calories: Work out your BMR and the daily calories to maintain your weight, with gentle options to lose or gain slowly, and a safe minimum. Adults only. Free.
- Due date calculator: pregnancy weeks and trimester: Work out your estimated due date from your last period or conception date, with your weeks of pregnancy, trimester and key dates. Free, no sign-up.
- Ovulation calculator: fertile window and next cycles: Find your estimated ovulation day, fertile window and next period, plus the next three cycles, from your last period, to plan a pregnancy. Free.
- Pharmacy margin calculator: profit and discount: Work out profit per unit, markup and margin for a pharmacy from cost and selling price or a target margin, plus what a discount does to profit. Free.
- Reorder point and safety stock calculator for pharmacies: Reorder point calculator: find safety stock and a suggested order quantity for a pharmacy from daily sales and lead time, with an expiry warning. Free.
- Clinic no-show cost calculator: Work out your clinic’s no-show rate, the revenue lost each month and year to missed appointments, what reminders could recover, and the break-even cost. Free.