At a high level, you can think of ‘epoch’ as the beginning of time in a sense, and in relation to BigFix, it can be helpful as a marker for when something was started/created. As it relates to BigFix Disaster Recovery, there are at least 2 components I can think of where it may come into play: 1) the BigFix database, 2) the Actionsite. In both cases, understanding the epoch can help with synchronization across components and defining a ‘source of truth’.
I hope that helps at least a little…beyond that, if you can provide more context on the question, we can perhaps provide more details or guidance.