* Returns a DATETIME string converted to the right timezone
* @param mixed The time to be converted
* @param string The timezone to be converted to. If null, the timezone will be determined based on user preference, or timezone chosen by the admin for the platform.
* @param string The timezone to be converted to.
* If null, the timezone will be determined based on user preference,
* or timezone chosen by the admin for the platform.
* @param string The timezone to be converted from. If null, UTC will be assumed.
* @return string The converted time formatted as Y-m-d H:i:s