Epoch

undefined:

An epoch is a grouping of headmates who came into existence during a specific time period.

Members in an epoch don’t have to be in a subsystem, layer, or any other kind of classification, but are grouped together by time-period.

Members of an epoch may or may not know each other better, be able to communicate with each other better, and other things often associated with system groups.

An epoch can be any size, and entire groups may also fall under the same epoch. The term can be used the same way terms like subsystem, system, and layer are.