Appointment.py

class Appointment(models.Model):

  # ... #

  def save(self, *args, **kwargs):
    update_series = kwargs.pop('update_series', True)
    super(Appointment, self).save(*args, **kwargs)
  
    if update_series and self.rrule:
      rrule = self.rrule.get_rrule()
      for date in rrule.between(self.start_time, self.start_time + timedelta(days=365 * 2)):
        appt = Appointment()
        appt.start_time = date
        appt.rrule = self.rrule
        appt.save(update_series=False)

        appt.services = self.services.all()