MAGETWO-72670: Deprecate wrapper methods for datetime handling

Author: OlgaVasyltsun

lib/internal/Magento/Framework/Stdlib/DateTime.php

@@ -79,6 +79,9 @@ public function isEmptyDate($date)
      * @param int $time
      * @return string The given time in given format
      *
+     * @deprecated
+     * @see Use Intl library for datetime handling: http://php.net/manual/en/book.intl.php
+     *
      * @codeCoverageIgnore
      */
     public function gmDate($format, $time)
@@ -92,6 +95,9 @@ public function gmDate($format, $time)
      * @param string $timeStr
      * @return int
      *
+     * @deprecated
+     * @see Use Intl library for datetime handling: http://php.net/manual/en/book.intl.php
+     *
      * @codeCoverageIgnore
      */
     public function strToTime($timeStr)