Changed date time format to RFC_3399 in VcsDriver

src/Composer/Repository/Vcs/VcsDriver.php

@@ -116,7 +116,7 @@ abstract class VcsDriver implements VcsDriverInterface
         $composer = JsonFile::parseJson($composerFileContent, $identifier . ':composer.json');
 
         if (empty($composer['time']) && $changeDate = $this->getChangeDate($identifier)) {
-            $composer['time'] = $changeDate->format('Y-m-d H:i:s');
+            $composer['time'] = $changeDate->format(DATE_RFC3339);
         }
 
         return $composer;