Well, I thought I'd be able to abandon this thread, but no...
I was just checking my calendar again, having done nothing more with the DST issue, had left the Automatic Network Time Sync
disabled, but
my appointments are once again showing an hour early!!!! 
I guess I'll try resetting to GMT and back again, but this is just so stinking ridiculous that I can't believe it.
unitmonster - is your Calendar still showing the correct times?
One minor consolation - my Holidays are at least staying on the correct dates. Whoop-de-doo!
ETA: I went into CDMA settings, switched Time Zone back to London/GMT, clicked OK, didn't reset, and switched it back to Eastern. Each time it indicated it would change appointments to the new time zone, and it took a little bit to do it each time.
After this (again, no reset), the Calendar again showed the correct times.
So somehow this is still getting screwed up by something, even when Auto Network Time Sync is disabled, so that may not be the triggering cause, or at least not the
only triggering cause.
Still a bunch of garbage...