What Does "AH" Mean After a Hijri Year — and How Are Hijri Dates Written?

Short answer: AH is the abbreviation for the Latin anno Hegirae, "in the year of the Hijrah" — the label for the Hijri era, the way CE/AD labels the Gregorian era. The U.S. Naval Observatory's Islamic calendar reference gives the start of the era as 1 Muharram, A.H. 1, corresponding to 16 July 622 C.E. in the Julian calendar. A four-digit Hijri year such as 1447 is therefore an era count, not a count of elapsed Gregorian years.

The notation you will actually see

AH or A.H. — anno Hegirae; the Hijri era. Usually written after the year: 1447 AH.
H — a shorter form used on some documents and stamps, as in 1447 H.
هـ — the Arabic-script equivalent, placed after the year.
CE / AD, or م in Arabic script — the Gregorian era, often printed alongside the Hijri date on Saudi paperwork.

A form that shows both eras is doing you a favor. One that shows a bare four-digit year starting with 14 is almost certainly Hijri.

In short: AH, H, and هـ all mean the same thing — this year number belongs to the Hijri era.

How to read a written Hijri date

Hijri dates are most often written day / month / year, so `15/8/1447` reads as the 15th of the eighth month, Sha'ban, in 1447 AH. Two habits save a lot of confusion:

Check the year first. A year in the 1400s is Hijri; a year in the 2000s is Gregorian. That one glance resolves most ambiguity without needing to know the field order.
Don't assume US month-first order. `3/10/1447` is far more likely to be day 3 of month 10 than month 3 of day 10.
Watch for month names instead of numbers, which removes the ambiguity entirely — see the twelve Hijri months in Arabic.

In short: read the year, then assume day-month-year unless the document says otherwise.

Why 1447 AH is not "1447 years ago"

This is the question behind searches like 1 Hijri is equal to how many years. The Hijri calendar is purely lunar: the Naval Observatory's Islamic calendar page describes twelve months of 29 or 30 days, giving a year roughly eleven days shorter than the Gregorian year, and its introduction to calendars sets purely lunar calendars apart from solar and luni-solar ones.

Shorter years accumulate faster, so the two era counts diverge:

Roughly 97 Gregorian years pass for every 100 Hijri years, following from that eleven-day annual difference.
The gap between the two year numbers therefore widens slowly over time rather than staying fixed.
Converting a specific date is not a matter of adding a constant — details are in converting Hijri dates to Gregorian.

For a worked example of one year mapped onto its Gregorian span, see what is the year 1446 in Islam; for the current count and how to verify it, see what Hijri year is it now.

In short: a Hijri year number counts lunar years, which run shorter than solar ones.

Who established the era?

The era takes its name from the Hijrah, and the official and astronomical references cited here document where the count begins — the epoch given above — rather than who decreed that counting should start there. We don't name a founder on this page, because the sources we cite don't; that question belongs to historical scholarship, and a general history reference is the right place to pursue it.

In short: the sourced fact is the epoch, not the authorship.

Checking a date against the official calendar

For Saudi official purposes, the published Umm al-Qura calendar is the reference for Hijri dates and conversions. If a date on a document and a date from a converter disagree by a day, that is a known and ordinary mismatch between calculated and announced month starts, not necessarily a mistake on the form.

Bottom line: AH marks the Hijri era counted from the Hijrah, with the epoch documented as 16 July 622 C.E. (Julian) — and because Hijri years are shorter, the year number runs ahead of the elapsed Gregorian time by a margin that keeps growing.