Date/Time: Use strict comparison in `is_new_day()`, add a unit test.

Props pbearne.
Fixes #46627.
Built from https://develop.svn.wordpress.org/trunk@45375


git-svn-id: http://core.svn.wordpress.org/trunk@45186 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/functions.php

@@ -797,7 +797,8 @@ function wp_get_http_headers( $url, $deprecated = false ) {
  */
 function is_new_day() {
 	global $currentday, $previousday;
-	if ( $currentday != $previousday ) {
+
+	if ( $currentday !== $previousday ) {
 		return 1;
 	} else {
 		return 0;

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-45371';
+$wp_version = '5.3-alpha-45375';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.