Yeah, I tried setting the clock to 2:20 - it doesn't BSOD at 2:21.
I'm trying to nail down when whatever it is gets set by rebooting at various times before 2:21. Roughly speaking, if I reboot 3 hours ahead, I still get the BSOD. If I reboot 1 hour ahead, I don't. So, very roughly, something is getting set up about 2 hours before the BSOD.
My hardware has been 100% unchanged since the upgrade to W10. The only change in the last few years has been to add 5.1 speakers - probably not significant.
A few years before that, my machine would hard crash if certain sectors got accessed on the C: drive. So I cloned it and I have been using it as my backup drive ever since. I thought this might be the cause of the crashes so I unplugged it and I still get the BSOD.
Now I'm learning how to read crash dumps...