Car clocks automatically updating to Daylight Saving Time

Have you tried going back in time and kidnapping a couple of whales?

The same signal might be picked up by clocks in different jurisdictions with different rules on DST. If you encode DST info into the time signal, you cause potential errors based on whether DST applies in the user’s jurisdiction or not. Same with time zones - you might have users in different time zones synching to the same signal. Good practice is therefore to simply broadcast a UTC signal and let time zone and DST offsets be handled decentrally based on the settings of the individual clocks.