@wordpress/date: Fix ordinal token (S), RFC2822 token (r), and timezo…

…ne offset handling (#39670)

* Add tests to wp-date for different format strings

* Fix failing wp-date tests

packages/date/src/index.js

@@ -136,11 +136,34 @@ let settings = {
 export function setSettings( dateSettings ) {
 	settings = dateSettings;
 
-	// Backup and restore current locale.
+	setupWPTimezone();
+
+	// Does moment already have a locale with the right name?
+	if ( momentLib.locales().includes( dateSettings.l10n.locale ) ) {
+		// Is that locale misconfigured, e.g. because we are on a site running
+		// WordPress < 6.0?
+		if (
+			momentLib
+				.localeData( dateSettings.l10n.locale )
+				.longDateFormat( 'LTS' ) === null
+		) {
+			// Delete the misconfigured locale.
+			// @ts-ignore Type definitions are incorrect - null is permitted.
+			momentLib.defineLocale( dateSettings.l10n.locale, null );
+		} else {
+			// We have a properly configured locale, so no need to create one.
+			return;
+		}
+	}
+
+	// defineLocale() will modify the current locale, so back it up.
 	const currentLocale = momentLib.locale();
-	momentLib.updateLocale( dateSettings.l10n.locale, {
-		// Inherit anything missing from the default locale.
-		parentLocale: currentLocale,
+
+	// Create locale.
+	momentLib.defineLocale( dateSettings.l10n.locale, {
+		// Inherit anything missing from English. We don't load
+		// moment-with-locales.js so English is all there is.
+		parentLocale: 'en',
 		months: dateSettings.l10n.months,
 		monthsShort: dateSettings.l10n.monthsShort,
 		weekdays: dateSettings.l10n.weekdays,
@@ -157,22 +180,19 @@ export function setSettings( dateSettings ) {
 		},
 		longDateFormat: {
 			LT: dateSettings.formats.time,
-			// @ts-ignore Forcing this to `null`
-			LTS: null,
-			// @ts-ignore Forcing this to `null`
-			L: null,
+			LTS: momentLib.localeData( 'en' ).longDateFormat( 'LTS' ),
+			L: momentLib.localeData( 'en' ).longDateFormat( 'L' ),
 			LL: dateSettings.formats.date,
 			LLL: dateSettings.formats.datetime,
-			// @ts-ignore Forcing this to `null`
-			LLLL: null,
+			LLLL: momentLib.localeData( 'en' ).longDateFormat( 'LLLL' ),
 		},
 		// From human_time_diff?
 		// Set to `(number, withoutSuffix, key, isFuture) => {}` instead.
 		relativeTime: dateSettings.l10n.relative,
 	} );
-	momentLib.locale( currentLocale );
 
-	setupWPTimezone();
+	// Restore the locale to what it was.
+	momentLib.locale( currentLocale );
 }
 
 /**
@@ -366,7 +386,18 @@ const formatMap = {
 	},
 	// Full date/time.
 	c: 'YYYY-MM-DDTHH:mm:ssZ', // .toISOString.
-	r: 'ddd, D MMM YYYY HH:mm:ss ZZ',
+	/**
+	 * Formats the date as RFC2822.
+	 *
+	 * @param {Moment} momentDate Moment instance.
+	 *
+	 * @return {string} Formatted date.
+	 */
+	r( momentDate ) {
+		return momentDate
+			.locale( 'en' )
+			.format( 'ddd, DD MMM YYYY HH:mm:ss ZZ' );
+	},
 	U: 'X',
 };
 
@@ -558,7 +589,7 @@ function buildMoment( dateValue, timezone = '' ) {
 		return dateMoment.tz( settings.timezone.string );
 	}
 
-	return dateMoment.utcOffset( settings.timezone.offset );
+	return dateMoment.utcOffset( +settings.timezone.offset );
 }
 
 /**