Ok, found some old cheat sheet in one of the manuals, changed the time. It worked. Seems to have changed all of them. Looks like someone tried to 'fix' it a month ago, not realizing the problems that would arise. I assumed it was related to the old DST dates, but I wasn't sure what they were.
Intercom lights up. Tried it again, picked up phone, *727, 111 and then busy signal.
