After 'connection assist', we should use the timestamp in the moat response
If I understand correctly, the plan for connection-assist is that some Tor Browser users are going to start doing a moat connection as one of their first steps, to learn how they best ought to connect in their country.
Part of the http response to whatever they're doing over moat will be a timestamp.
If Tor Browser thinks it is a wildly different time than that timestamp, we could do something smart like tell the user. This will help with issues like "obfs4 won't bootstrap with skewed clock" (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/obfs4/-/issues/32439), which especially bites Tails users but really can bite anybody.
We had/have plans to do this learning inside Tor, but (a) we've never quite done it, and now Arti is the new hotness so old-Tor probably won't ever get that feature, and (b) if obfs4 can't handshake, Tor will never proceed and never know why.
(There is a danger here, in that we're creating yet more critical infrastructure for ourselves, in the sense that if somehow the moat server thinks it's last week, we could trigger millions of pop-ups across the world and confuse millions of users. Still seems like a net win, but we should carefully compare consequences. :)