Daylight Saving command

What exactly is the Daylight Saving command (H’AF’) doing ?
According to the docs a value of 0 disables daylight saving and 1 enables it. But if I use the sync clock button in Velbuslink, it sends the command with a value of 1 and it is now winter time. I would expect a value of zero during winter time.
I had some problems with program steps in the week around the summer to winter time switch, with program steps being 1 hour out of sync. I use a script that checks if DST has changed based on OS time executed every night and uses this Daylight Saving (DST) command to set the value to 1 in summer and 0 in winter.
When I change the DST now a few weeks after the switch to winter time, it doesn’t matter if its set to 1 or 0, the program steps are always correct. So what exactly is this command doing ?

  • Does it set or reset an offset of 1 hour ?
  • Does it recalculate the timetables only when the DST changes and nothing in any other period ?
  • Something else ?

This is not clear from the docs.