urbit/pub/doc/arvo/time.md

%time

Our simple timer.

It allows vanes and applications to set and timer events, which are managed in a simple priority queue. %time produces effects to start the unix timer, and when the requested %time passes, unix sends wake events to %time, which time routes back to original sender. We don't guarantee that a timer event will happen at exactly the %time it was set for, or even that it'll be particularly close. A timer event is a request to not be woken until after the given time.

%eyre uses %time for timing out sessions, and %clay uses %time for keeping track of time-specified file requests. %ames should probably use %time to keep track of things like network timeouts and retry timing, but it currently uses its own alarm system.