If you try to exchange weeklies with the Manage Currency box, you get, "this item can no longer be exchanged" for every weekly exchange except the 40 stack and the 300% XP scroll. 

Those are always delayed until later in the patch day - or maybe weekly reset day?  It's not reset time (00:00 UTC), but a few hours after that.

Has anyone identified exactly what the coelecanth exchange reset time is?

edit: Just now checked, I was able to exchange.