How long PLC powered off

A GE Fanuc Micro PLC in India suffers from multiple power outs. Is there a %S system var or other technique for knowing that a reboot occurred? A standard way to know how long it has been off?

(I could set registers with the current timestamp and somehow use that?)

How are you going to capture a timestamp of when the power went off?

%S001 is a first scan contact. %S002 is a last scan contact.

According to GFK-0467, %S002 is "reset from 1 to 0 when the current sweep is the last sweep".

Or just keep overwriting a timestamp-register every scan or with a timer, and then on first scan minus last timestamp from current time and add the difference to a register/array. Repeat.

Power OFF

I am 100% agree with steve bailey.

Steve Baily... how does the PLC know it is dying to be able to set the flag? Really, what does LAST SCAN mean? I assume it means that a STOP request has been recognized so it gives one more sweep to let the code prepare if needed. But POWER failure? (Unless it has a long holdup time (like two scans worth) in the powersupply and the powersupply gives notice that the input has disappeared.)

Scanning by time difference seems possible -- each scan (or every sec or minute) move the RTC timestamp array to a saved location. Then at FIRST SCAN you check and compare how much time elapsed.