Why there is no fixed offset
A Hijri year is about 11 days shorter than a Gregorian one, so you cannot add or subtract a fixed number of years. 1447 AH began on 26 June 2025 and 1448 AH on 16 June 2026, so the Islamic New Year moved ten days earlier in a single year.
Estimating the year
Hijri → Gregorian: Gregorian year ≈ (Hijri year × 0.970229) + 621.5643
Gregorian → Hijri: Hijri year ≈ (Gregorian year − 621.5643) × 1.030684
0.970229 is the ratio of the mean Hijri year to the Gregorian year; 621.5643 places the start of the Hijri era on the Gregorian timeline.
| Input | Calculation | Result | Reality |
|---|---|---|---|
| 1447 AH | 1447 × 0.970229 + 621.5643 | ≈ 2025.5 | 1447 ran from mid-2025 to mid-2026 |
| 2026 CE | (2026 − 621.5643) × 1.030684 | ≈ 1447.5 | 2026 spans late 1447 and early 1448 |
| 1419 AH | 1419 × 0.970229 + 621.5643 | ≈ 1998.3 | 1419 began in April 1998 |
Why the formula can’t convert a specific day
Hijri months are 29 or 30 days depending on the moon, while the formula uses an average, so a specific date can be off by a day or two. The exact method: look up the Gregorian date on which the Hijri month begins, then add the day number. Example: 1 Ramadan 1447 AH is 18 February 2026, so 15 Ramadan 1447 AH = 18 February + 14 days = 4 March 2026.
Exact conversion with a table
- Open the Hijri Calendar at the right year.
- Read the Gregorian start date of the month.
- Add the day number minus one.
Or use the Hijri–Gregorian Converter, which does exactly this with Umm al-Qura tables. The formula is fine for estimating the year of a historical event; for birth dates, contracts and transactions use the table or converter, and rely on the date written on official documents.
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