Document the Umm al-Qura range currently known in browsers in terms of ISO/Gregorian

[hsivonen]

Description

Mentions what the range of KACST-provided Umm al-Qura month length data in browser (as of October 2025) is in terms of the ISO / Gregorian calendar.

Motivation

This helps readers who aren't used to working with Hijri calendars but are familiar with the Gregorian calendar get an idea of the covered time span.

Additional details

For verifying:

• Browsers use ICU4C and/or ICU4X.
• The year range being inclusive of 1600 AH can be seen for ICU4X at https://github.com/unicode-org/icu4x/blob/329aa64d04e229c47f04879204a811156eff9576/components/calendar/src/cal/hijri/ummalqura_data.rs and for ICU4C at https://github.com/unicode-org/icu/blob/1bf6bf774dbc8c6c2051963a81100ea1114b497f/icu4c/source/i18n/islamcal.cpp#L264
• The Gregorian correspondence can be checked by running (10 instead of 11 for month due to the oddity of Date):

var fmt = new Intl.DateTimeFormat("en-US-u-ca-islamic-umalqura");
console.log(fmt.format(new Date(Date.UTC(1882, 10, 11))));
console.log(fmt.format(new Date(Date.UTC(1882, 10, 12))));
console.log(fmt.format(new Date(Date.UTC(2174, 10, 25))));
console.log(fmt.format(new Date(Date.UTC(2174, 10, 26))));

[github-actions]

Preview URLs

• /en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/supportedValuesOf

(comment last updated: 2025-10-07 08:54:50)

[Josh-Cena]

Nice, thank you!