If the power is cutting out without warning, it's probably the cause of the issue with the time and date being lost.  You likely should contact Dell about the issue and arrange a warranty repair.  
Hey all, I have a Latitude 9420 and in the BIOS error log I see a few entries about the time and date not being set. In the past I would equate this to a CMOS battery issue. I've opened the laptop to check/replace the battery but I can't for the life of me find it. Does this model not have one? Any help is appreciated. Neil
Dell Latitude 9420 no CR2032 battery?