they put a millisecond clock with a 32-bit register, in a plane, and it overflows https://www.theregister.co.uk/2020/04/02/boeing_787_power_cycle_51_days_stale_data/

2^32 = 4,294,967,296
51 * 24 * 60 * 60 * 1000 = 4,406,400,000