This message will appear when the internal battery, which is responsible for keeping time is dead or not working properly.  The instrument can function properly only the time stamp and time keeping of the internal clock would be effected.  Please see below for a guide for our reps. 

Units with serial number < 9760685 will have older designed boards that require the battery to be replaced between the boards.

Newer units > 9760685 should have the new board with bigger battery and allows for easy changing of the battery.

Serial < 976068

Replace with newer boards part # 39587 and battery #39907

The old battery is item number 39416, which is a 3V coin battery CR1220.
> 9760685