What is Date & Time Localization?
Date and time localization is rendering temporal values the way each locale expects: component order (day before month or the reverse), separators, translated month and day names, 12-hour versus 24-hour clocks, and which day starts the week. The same instant renders as 07/09/2026 for a US user and 09/07/2026 for a French one, which is exactly why raw format strings are dangerous.
The robust approach is to store instants in UTC and localize only at the presentation edge, combining two independent transformations: time zone conversion for the user's location and locale-aware formatting for their language. PHP's IntlDateFormatter draws patterns from CLDR, and Carbon wraps this ergonomically with locale-aware output via isoFormat() and translatedFormat(). The two steps are independent: a Spanish speaker in New York needs Spanish formatting applied to New York local time.
Prefer semantic format selection, "a long date", "a short date with time", over hardcoded patterns, so each locale supplies its own convention. Relative formats ("3 days ago") also need translation, and Carbon localizes those through the same locale machinery.
use Carbon\Carbon;
$date = Carbon::parse('2026-07-09 14:30', 'UTC');
$date->locale('es')->isoFormat('LL'); // "9 de julio de 2026"
$date->locale('de')->isoFormat('LLLL'); // "Donnerstag, 9. Juli 2026 14:30"
$date->locale('fr')->diffForHumans(); // "il y a ..." style output