docs: def _update_gmt(self):
          """
          Based on timezone and start date, the GMT card is updated
          """
          if self.simulation_start is not None:
              # NOTE: Because of daylight savings time,
              # offset result depends on time of the year
              offset_string = str(self.simulation_start.replace(tzinfo=self.tz)
                                  .utcoffset().total_seconds()/3600.)
              self._update_card('GMT', offset_string)