diff --git a/MD_STD.php b/MD_STD.php
index 59e4848..ec49462 100644
--- a/MD_STD.php
+++ b/MD_STD.php
@@ -163,7 +163,7 @@ class MD_STD {
      */
     public static function strtotime(string $datetime):int {
 
-        $output = strtotime($datetime);
+        $output = \strtotime($datetime);
         if ($output === false) throw new MDInvalidInputDate("Invalid input date {$datetime}.");
         return $output;