Many thanks Brendan, got them now. I was trying to make 23 work with decko, which is why I got nowhere with 27.
I'm still unhappy about the parsing of 23, Dec 0 is definitely the day
before Nov 31, not the one after; and I cannot see why we pick the last letter out of anger. On the other hand, I see red backwards and I wonder if that's a way to break the clue down, although I still don't get the rest.
Today's Everyman was a stroll in the park by comparison! Many thanks to all the contributors here, who are both a great help and a reassurance that I'm not the only one struggling. I'm only sorry that I don't look frequently enough to help on the rare occasions when someone asks about a clue that I've got!