Driving home yesterday, I noticed the digital clock was showing the wrong time by an odd amount.

 

So once home I took the manual indoors to have a read of how to adjust it, but there’s no mention of this.

 

But when I went out in the car again, the correct time was showing. 
 

A quirk of GPS/internet or whatever the car connects to?

If you have navigation then the time can be set to get from the GPS signal, alternatively set it manually in the infotainment unit. There may be an option to get the time from RDS but not sure and will depend on the head unit.

There is an option in the settings to turn on the time change 

I have had this a couple of times where the clock is showing some random time and then it quickly resolves itself cycling the ignition of and on. 

 

2016 owned from 6 months old with Amundsen head unit. 

Same in my 2018 SE.  The clock seems to have a mind of its own then sorts itself out when the car is next started.  Also I had an occasion when the trip meter reset itself to zero and the clock to 12 o'clock.  Dealer had a look and messed with the software but the clock thing still happens now and again.  I just ignore it now.

Basically what you are seeing is an unset clock without being synchronised. What should probably happen is that the value of time from the GPS signal should be written to memory but it occasionally isn't. The situation is made worse if you have a low battery on your car (MIB occasionally internally resets time and date) causing odderites.