Read the current time in seconds since Jan, 1970, aka Epoch or Unix time. This value is calculated from the 80 MHz crystal, not the RTC 32 kHz crystal. Non-pro devices do not have a real time clock, so the reported time is either seconds since device startup or the time reported by the network time protocol over Ethernet. Pro devices have a real time clock that will be used to initialize this register at startup, the time can then be updated by NTP.