Good tip, thanks. I’d left advanced settings for all shields to defaults (typically “chest”), but have now changed most of them to ask as the first choice per your suggestion. Guess the two clock-sync apps work just enough differently from each other that one triggers avast but the other doesn’t.
I’ll go back and reinstall WebTime and try again; I prefer that one (they’re both freeware) since it gives you a good built-in menu-selection of remote time servers whereas the other one defaults to using a random server. I’m certainly not concerned with an error of (typically) microseconds … mostly it lets me use the computer’s clock as a reference for the odd time when we lose power and all other clocks in the house need reset.
(Edit/update) Nope, no luck with WebTime even with the changed shield settings. Since nothing else on my system has changed in quite a while, other than updating avast, and I don’t believe in coincidences of timing (at least not on computers), it seems like a fair guess that it’s somehow tied in to the changes from 5.1 to 6.