why does the time advance 5 hours on my apple 3 cellular watch when in my volvo?

I have a few suggestions which might help you work out what is causing this. In the order I think of them, so pick the easy ones first...

• Does the problem still occur if you are in the car but your iPhone is not actively linked to the car’s Bluetooth? Try with the ignition switch in different positions, off, accessory, engine running, etc.
• Is your Volvo one of the models equipped with integrated WiFi and/ or cellular which might be causing chaos?
• Does the problem occur if your watch is not connected to your iPhone (phone off?) when you would otherwise expect it to happen?
• Where are you and what time zone applies? I’m thinking time zones, 5 hours, where in the world does your watch think it is?
• Did you by any chance attempt to pair your watch direct to the car’s Bluetooth?

That might be the clue we need. Does your watch jump to UTC? (5 hours ahead of you, so your local 10am would be 3pm on the watch).

Theory: I think you have connected your iPhone at least once to the car WiFi which makes it a known connection available to the watch, so the watch will connect over WiFi and probably gets an incorrect time sync from the car. To test this hypothesis you could swipe up on the watch to open Control Center, and look at the WiFi button (top right). If it has a blue background it has an active connection probably to the car. Regardless, tap it to disable WiFi on your watch (button now has a black background) and see if the watch behaves any better.

Ok! Now you know how it gets broken, and how to demonstrate the problem. It looks like the car connectivity is either wrongly configured, or is ignoring time zone in its time signals. The likely sources are the cellular signal which supports the car’s connectivity, time signals embedded in radio broadcasts for the infotainment system, or picked off from the car’s GPS and navigation system. At least the first and probably the second should have time zone in their received time data.

The next task is to think of a permanent solution. If leaving WiFi routinely off is acceptable to you that is simple enough, just remember to enable it again when it comes to software upgrade time. If you need WiFi on the watch for your daily usage it might be worth digging into the car’s menus, there might be a time zone configuration in there somewhere. You could also consult the dealer, a new car feature should not break normal operation on your watch And there might be something they can fix in workshop.