# Born January 1, 1980 — Hijri & All Calendars — Hijri Age Calculator

> 1 Jan 1980 in Hijri is 12 Safar 1400 AH — the start of the 15th Hijri century. See all 8 calendar conversions including Persian 1358 Dey 11.

- **Answer:** 1 Jan 1980 = 12 Safar 1400 AH
- **Category:** Date & Time
- **Interactive calculator:** https://youcalc.com/en/date-time/multi-calendar-age/born-in-1980-hijri-date/
- **Price:** Free, no sign-up required
- **Full calculator:** [Hijri Age Calculator](https://youcalc.com/en/date-time/multi-calendar-age/)
- **Pre-filled inputs:** `md=convert&sc=gregorian&by=1980&bm=1&bd=1`

| Metric | Value |
| --- | --- |
| Gregorian | 1980-01-01 |
| Hijri (Islamic) | 1400-02-12 |
| Persian (Solar Hijri) | 1358-10-11 |
| Julian | 1979-12-19 |
| Hebrew | 5740 Tevet 12 |


## Overview

January 1, 1980 maps to the 12th of Safar 1400 AH — making 1980 a historically significant Hijri birth year, as anyone born in the first months of 1980 was born in the 14th Hijri century (year 1399–1400) and turned Hijri year 1 at the very turn of the new century. The year 1400 AH began on November 9, 1979 in the Gregorian calendar. This is a popular query for those interested in Hijri century milestones.

## Method

Every date is reduced to a Julian Day Number (JDN), a continuous integer count of days since a fixed epoch, and every output is derived from that single pivot. The Gregorian, Julian and tabular Islamic conversions are hand-rolled from the standard algorithms (Fourmilab / US Naval Observatory): the Gregorian and Julian use the classic civil-date formulas, and the tabular Hijri uses the 30-year cycle with 11 leap years and the leap rule ((year × 11) + 14) mod 30 < 11, anchored to the epoch JDN 1948439.5 (1 Muharram AH 1 = Friday 16 July 622 CE in the Julian calendar). The Hebrew, Persian, Indian (Saka), Ethiopian and Chinese calendars are read through Intl.DateTimeFormat's ICU calendars at the civil noon of each JDN, which yields an exact year and day; the total days lived is simply the difference of the two JDNs, so it is identical across calendars. Age in years is computed by counting completed calendar-year anniversaries up to the as-of date, clamping to the last valid day when a birthday lands on a date that does not exist that year (such as 29 February). The Hijri-drift figure compares the mean tabular Hijri year (10631 ÷ 30 ≈ 354.367 days) with the mean Gregorian year (365.2425 days), a deficit of about 10.876 days per year, and reports the approximate extra Hijri years your age accumulates. "Today" is computed at local civil midnight in your time zone, after the page mounts, so the default as-of date is correct wherever you are without baking a build-time date into the page.

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## Sources

- https://aa.usno.navy.mil/faq/islamic
- https://www.fourmilab.ch/documents/calendar/
- https://en.wikipedia.org/wiki/Tabular_Islamic_calendar

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