diff --git a/wp-includes/SimplePie/Parse/Date.php b/wp-includes/SimplePie/Parse/Date.php
index 88e46e0309..52fea21efe 100644
--- a/wp-includes/SimplePie/Parse/Date.php
+++ b/wp-includes/SimplePie/Parse/Date.php
@@ -542,8 +542,8 @@ class SimplePie_Parse_Date
 	 */
 	public function __construct()
 	{
-		$this->day_pcre = '(' . implode(array_keys($this->day), '|') . ')';
-		$this->month_pcre = '(' . implode(array_keys($this->month), '|') . ')';
+		$this->day_pcre = '(' . implode('|', array_keys($this->day)) . ')';
+		$this->month_pcre = '(' . implode('|', array_keys($this->month)) . ')';
 
 		static $cache;
 		if (!isset($cache[get_class($this)]))
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 9188606035..e7ed517a6b 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-46259';
+$wp_version = '5.3-alpha-46260';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.