A lunar calendar, and what that changes
The Hijri calendar counts from the Hijra, the Prophet Muhammad's migration from Mecca to Medina in 622 CE — which is what AH, anno Hegirae, refers to. Its twelve months follow the moon rather than the sun, so a Hijri year runs about 354 days against the Gregorian 365.
That eleven-day difference is the reason Ramadan moves through the seasons over a lifetime rather than staying put, and it is also why the gap between the two year numbers is not fixed. The calendar started 622 years later but runs faster, so the two numbers are slowly converging.
Worked examples
1 January 2000 on the Gregorian calendar converts, on Umm al-Qura, to 24 Ramadan 1420 AH. Going the other way, 1 Shawwal 1420 AH — the first day of Eid al-Fitr that year on this calendar — lands on 8 January 2000, seven days later, because the rest of Ramadan and the start of Shawwal fill that gap.
Try converting 30 Safar 1447 and the page reports the date does not exist: Safar that Hijri year has only 29 days, so there is no 30th. Ask for 29 Safar 1447 instead and it converts normally. This is not a bug — it is the calendar's own shape, and the point of checking rather than assuming a month always has 30 days.
Why this page asks which calendar you mean
There is no single Hijri calendar, and a converter that pretends otherwise is giving you one answer out of several without telling you. Three conventions are offered here:
| Convention | What it is | Use it when |
|---|---|---|
| Umm al-Qura | The Saudi civil calendar, based on astronomical calculation for Mecca | Almost always — it is the default and what most official conversions mean |
| Tabular, civil | A pure arithmetic calendar with a 30-year leap cycle, Friday epoch | Historical work and software that specifies it |
| Tabular, astronomical | The same arithmetic with the epoch one day earlier | Some astronomical and academic sources |
Whichever you pick, the result panel shows what the other two say for the same day, because a difference of one day is exactly the sort of thing worth seeing rather than discovering later.
Reading the result
Convert a date and the primary card shows the answer — the calendar
you did not type into — with the month spelled out, for example
24 Ramadan 1420 AH. The secondary card restates what
you typed, in the same wording, so you can check it was read the
way you meant. Below both, a details list adds the day of the week,
the ISO date, how many days are in that Hijri month, and what the
two conventions you did not pick say for the same day — so a
one-day spread between Umm al-Qura and the tabular calendars is
visible immediately rather than found later by comparing two
separate lookups.
The thing no converter can do
None of these is the same as the date announced where you live. Many countries begin a month on a local sighting of the new crescent moon, which depends on your latitude, the time of sunset and whether the sky is clear. Two countries can start the same month on different days, and the same country can differ from a calculated calendar by a day in either direction.
That is not a shortcoming of the arithmetic — it is an observation, and observations cannot be computed in advance. For a religious obligation tied to a specific date, the announcement from your local authority is what counts, not this page or any other.
The twelve months
Muharram, Safar, Rabi al-Awwal, Rabi al-Thani, Jumada al-Awwal, Jumada al-Thani, Rajab, Shaban, Ramadan, Shawwal, Dhu al-Qidah and Dhu al-Hijjah. Each has 29 or 30 days, and which is which changes from year to year — that is what following the moon means. It is also why the converter will sometimes tell you a date does not exist: asking for day 30 of a month that had 29 days that year is asking for a day that never happened.
Where the conversion comes from
The page does no calendar arithmetic itself. Conversions are performed by the internationalisation library built into your browser, maintained by the Unicode Consortium, which is also what your operating system uses. Umm al-Qura in particular is a published table rather than a formula, so reimplementing it by hand would mean copying that table and hoping — precisely the kind of quiet error this site tries not to ship.
The reverse direction is not offered by that library, so it is solved by searching for the day whose forward conversion matches what you typed, and confirming the match exactly. Nothing is rounded, and nothing is approximated.
Common mistakes
- Treating any calculated calendar as the announcement date. All three conventions here are calculation. The date your mosque or country announces for Ramadan or Eid can be a day earlier or later, because it depends on moon sighting.
- Assuming a 622-year gap. The Hijri calendar started 622 years after the Gregorian one but its years are shorter, so the numeric gap shrinks over time — it is not a fixed offset you can add or subtract.
- Entering day 30 without checking the month length. Hijri months are 29 or 30 days depending on the year, unlike Gregorian months, which are always the same length. Use "Use today" or try a smaller day number if 30 is rejected.
Related tools
To work out an age or anniversary rather than convert a single date, see the Hijri age calculator, which counts elapsed years directly in the Hijri calendar rather than converting a Gregorian age. For the Solar Hijri calendar used in Iran and Afghanistan — a different calendar despite the similar name — see the Shamsi date converter.