<?php use DateTime; function datetimeTimestampToString($timestamp) { $datetimeObject = new DateTime("@$timestamp"); // will supposedly have the timezone set to UTC. // The spec requires exactly 'GMT' without numeric offset, so we cannot use DateTime::RFC1123. $datetimeString = $datetimeObject->format("D, d M Y H:i:s") . " GMT"; return $datetimeString; } function datetimeStringToTimestamp($datetimeString) { // Be tolerant and allow any RFC1123 formatted datetime string. $datetimeObject = DateTime::createFromFormat(DateTime::RFC1123, $datetimeString); $timestamp = $datetimeObject->getTimestamp(); return $timestamp; }