protected function encodeDateTime(DateTime $value = null) {
        return null === $value ? "" : $value->format(self::DATETIME_FORMAT);
    }
protected function encodeDateTime(DateTime $value = null) {
        return null === $value ? "" : $value->format(self::DATETIME_FORMAT);
    }
protected function encodeDateTime ( DateTime $ value = null ) { return null === $ value ? "" : $ value -> format ( self :: DATETIME_FORMAT ) ; }
Encode a datetime value.

@param DateTime $value The value.
@return string Returns the encoded datetime value.
Encode a datetime value .