We had a car in today with the same issue.
Carried out a major service and Ashley’s last job was to reset the service light.
The date and time were way behind, so Ashley set the date to the correct one before resetting the service token but it wouldn’t take.
We analysed the stored service tokens and you could clearly see that service token 4 (year 8) was corrupt as it had the month as 64...not a valid date. It was set twice from the data at the same mileage as the first attempt was done after a battery disconnect we think and the time zeroed out to 1/1/2000.
All the previous services were carried out via the main dealer!...so it’s not the service tool, it’s the operator not setting the clock and will brick it wether it be factory Diagnosi or aftermarket tool.
We then looked at another GTS that had a working service reset by us and what happens is you can not reset the date and time to before that of the last service reset.
Screw the reset and you screw the date and time.
Is there another fix than replacing the dash? I just got my car from my independent shop, obviously the technician that used the reset tool screwed it up. When I got the car, the date was 2091 and impossible to change. I did a battery reset, it went to 2000 and still impossible to change
Not very optimistic about ever getting my date/time back...