This read-write EpochTime value holds the ComPort's own clock as seconds elapsed since 1970. Keeping this synchronized matters because alarm and event timestamps generated by the STU (like stuAlmTime) are only meaningful if the device's own clock is accurate. For example, after replacing a STU's battery-backed clock circuit, an NMS would write the correct value to stuEpochTime so subsequent alarm timestamps line up with the rest of the network's event log.