IntlDateFormatter for December 30/31st 2024 returns "December 30/31st 2025" (same for 2026 and so on)

[bohwaz]

Description

The following code:

<?php
date_default_timezone_set('Europe/Paris');

$date = new DateTime('2024-12-30 00:00:00');
$format = 'd MMMM YYYY';
echo IntlDateFormatter::formatObject($date, $format, 'fr_FR') . PHP_EOL;
echo IntlDateFormatter::formatObject($date, $format, 'en_NZ') . PHP_EOL;

Resulted in this output:

30 décembre 2025
30 December 2025

But I expected this output instead:

30 décembre 2024
30 December 2024

This is the same with December 31st.

Same with 2025-12-30: reports as 2026.

It is even weirder with 2026-12-30:

<?php
date_default_timezone_set('Europe/Paris');
$date = new DateTime('2026-12-30 00:00:00');
$format = 'd MMMM YYYY';
echo IntlDateFormatter::formatObject($date, $format, 'fr_FR') . PHP_EOL;
echo IntlDateFormatter::formatObject($date, $format, 'en_NZ') . PHP_EOL;

Returns:

30 décembre 2026
30 December 2027

PHP Version

8.4.1

Operating System

Debian Bookworm

[bohwaz]

It's not just my Debian setup apparently: https://3v4l.org/qQeKL

[bohwaz]

Ah! didn't see YYYY was different from yyyy, nevermind :)

[heiglandreas]

Yeah. Contrary to the date syntax, the Yis the year of the ISO-Week in ICU. For theyear you want y

See https://unicode-org.github.io/icu/userguide/format_parse/datetime/#datetime-format-syntax

[bohwaz]

Yup my error came from the fact that I copied this date format string from a couple lines below where we actually want the year matching the ISO week :)

Thanks!