protected function convert_string( $value ) {

		$format = $this->input_data[ 'format' ];
		$date   = \DateTime::createFromFormat( $format, $value );

		// Invalid dates can show up as warnings (ie. "2007-02-99") and still return a DateTime object.
		$errors = \DateTime::getLastErrors();
		if ( $errors[ 'warning_count' ] > 0 ) {
			$this->error_code = Error\ErrorLoggerInterface::INVALID_DATE_FORMAT;

			return FALSE;
		}

		return $date;
	}