  Even in the absence of clocks, time bounds on the duration of actions enable
the use of time for distributed coordination. This paper initiates an
investigation of coordination in such a setting. A new communication structure
called a zigzag pattern is introduced, and shown to guarantee bounds on the
relative timing of events in this clockless model. Indeed, zigzag patterns are
shown to be necessary and sufficient for establishing that events occur in a
manner that satisfies prescribed bounds. We capture when a process can know
that an appropriate zigzag pattern exists, and use this to provide necessary
and sufficient conditions for timed coordination of events using a
full-information protocol in the clockless model.
