diff --git a/wp-includes/feed.php b/wp-includes/feed.php
index 3c88b4e1ec..ce4f1acdf4 100644
--- a/wp-includes/feed.php
+++ b/wp-includes/feed.php
@@ -683,7 +683,13 @@ function get_feed_build_date( $format ) {
 	}
 
 	// Determine the maximum modified time.
-	$max_modified_time = mysql2date( $format, max( $modified_times ), false );
+	$datetime = date_create_immutable_from_format(
+		'Y-m-d H:i:s',
+		max( $modified_times ),
+		new DateTimeZone( 'UTC' )
+	);
+
+	$max_modified_time = $datetime->format( $format );
 
 	/**
 	 * Filters the date the last post or comment in the query was modified.
diff --git a/wp-includes/version.php b/wp-includes/version.php
index f5aa671dbc..27d7715eb8 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3.1-alpha-46773';
+$wp_version = '5.3.1-alpha-46774';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.