The epoch is the date & time that the minimum value of that field refers to. For Unix derived or inspired machines it’s typically the Unix epoch of 00:00:00 on

The epoch is the date & time that the minimum value of that field refers to. For Unix derived or inspired machines it’s typically the Unix epoch of 00:00:00 on January 1, 1970. This means that a timestamp of “0” refers to that date and time, and increases at whatever granularity a timestamp value maps to. If you bake the epoch into the device at the factory as being the date of manufacture and your timestamp value has 20 years worth of granularity then you get a 20 year life from manufacture time before the timestamp rolls over to 0 again. If you’re going to use more space keep a rollover counter you may as well just add more bits to your timestamp field instead, since every bit doubles the amount of time that field can represent.