There is one way... puke the battery and see what it resets too. Hopefully it’s 12 hour so pull the battery and reconnect at 12.
is there a 3rd button on the left side to hold to make the H and M buttons work?
I have found that option yes but from what I can tell all it does is stops the time from displaying on the main navi screen. The difference with the newer car is that they have a more traditional LCD screen at the top of the dash that displays the time — even has the old school little H and M buttons for changing the time, but they do nothing.