Now that you mention it, isn't this what "Zulu Time" is for? Once in flight it seems that the only time that is relevant is GMT (Zulu). Am I right?
It's true as written.
I work for the Air Force. I am a Software Safety Engineer (on a different program I hasten to add!).
We are now trusting SW produced by industry by 'Extreme Programming', or 'Scrum' techniques to perform safety critical functions. This is what happens.
The FAA has lots of SW design and test stipulations to prevent this on commericial planes, but the military went to a 'best industry practices', vice tight SW design/test regs under 'Acquisition Reform'.
This kinda thing happens occasionally and will get more frequent....
I'm not seeing it either. I can't speak for comms or other systems, but for navigation, every GPS system I've seen gets its date/time stamps from the satellites, in GMT. The Date Line doesn't mean squat when you're using GMT.