Formatting & Plurals|

plural selects the CLDR category via Intl.PluralRules — correct for any BCP-47 locale. Provide a <key>_plural entry as a JSON object of categories:

en/de collapse to one/other; Slavic locales add few/many; Arabic uses the full set. Without a _plural object the base string is returned as-is — fail-honest, no anglocentric +'s' guessing.

formatNumber, formatDate, and formatRelativeTime wrap the matching Intl API for the active locale and take the same options it does — so anything Intl.NumberFormat / Intl.DateTimeFormat / Intl.RelativeTimeFormat accepts works here.

formatTimeAgo(date) is the exception: it composes a relative string from registered time.* translation keys (and falls back to formatDate past ~30 days), so it takes no options and needs those keys registered. The other three are pure Intl wrappers.

These values are formatted by the real useI18n() hook against the active site locale (en). Switch the language with the locale switcher in the sidebar and watch them re-render.