Date/Time: Introduce wp_timezone_string() and wp_timezone() for unified timezone retrieval.

* `wp_timezone_string()` retrieves the timezone from current settings as a string. Uses the `timezone_string` option to get a proper timezone if available, otherwise falls back to an offset.
* `wp_timezone()` retrieves the timezone from current settings as a `DateTimeZone` object. Timezone can be based on a PHP timezone string or a `±HH:MM` offset.

Props Rarst, remcotolsma, johnjamesjacoby, rmccue.
Fixes #24730.
Built from https://develop.svn.wordpress.org/trunk@45853


git-svn-id: http://core.svn.wordpress.org/trunk@45664 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/functions.php

@@ -74,7 +74,49 @@ function current_time( $type, $gmt = 0 ) {
 }
 
 /**
- * Retrieve the date in localized format, based on a sum of Unix timestamp and
+ * Retrieves the timezone from current settings as a string.
+ *
+ * Uses the `timezone_string` option to get a proper timezone if available,
+ * otherwise falls back to an offset.
+ *
+ * @since 5.3.0
+ *
+ * @return string PHP timezone string or a ±HH:MM offset.
+ */
+function wp_timezone_string() {
+	$timezone_string = get_option( 'timezone_string' );
+
+	if ( $timezone_string ) {
+		return $timezone_string;
+	}
+
+	$offset  = (float) get_option( 'gmt_offset' );
+	$hours   = (int) $offset;
+	$minutes = ( $offset - $hours );
+
+	$sign      = ( $offset < 0 ) ? '-' : '+';
+	$abs_hour  = abs( $hours );
+	$abs_mins  = abs( $minutes * 60 );
+	$tz_offset = sprintf( '%s%02d:%02d', $sign, $abs_hour, $abs_mins );
+
+	return $tz_offset;
+}
+
+/**
+ * Retrieves the timezone from current settings as a `DateTimeZone` object.
+ *
+ * Timezone can be based on a PHP timezone string or a ±HH:MM offset.
+ *
+ * @since 5.3.0
+ *
+ * @return DateTimeZone Timezone object.
+ */
+function wp_timezone() {
+	return new DateTimeZone( wp_timezone_string() );
+}
+
+/**
+ * Retrieves the date in localized format, based on a sum of Unix timestamp and
  * timezone offset in seconds.
  *
  * If the locale specifies the locale month and weekday, then the locale will

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-45852';
+$wp_version = '5.3-alpha-45853';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.