An offset is simply the difference between UTC and localtime, whereas the time zone is a named set of rules describing how the offset changes over time.
Therefore a time in time zone 0 (GMT at the time, as there was no UTC yet) would have an odd timeoffset when represented as localtime for Yekaterinburg (Russia).
Links nodes not be necessary to send messages to the each other, known of the two nodes 'time can determine the scope of the third node's offset and drift, then determine its localtime.