Return UTC datetime from timestamp in config file.

        :param section: Config section
        :param option: Config option
        :param fallback: Fallback/default value
        :return: Datetime in UTC
        :rtype: :class:`datetime.datetime`

def get_datetime(self, section, option, fallback):
        """
        Return UTC datetime from timestamp in config file.

        :param section: Config section
        :param option: Config option
        :param fallback: Fallback/default value
        :return: Datetime in UTC
        :rtype: :class:`datetime.datetime`
        """
        try:
            s = self[section][option]
            try:
                # If stored as timestamp
                return datetime.utcfromtimestamp(int(s))
            except ValueError:
                # Otherwise parse ISO format
                return datetime.strptime(s, self.DATETIME_FMT)
        except (KeyError, ValueError):
            return fallback