What if a global operation is dependent on some basic procedure which is vulnerable to failure or sabotage? There needs to be duplication and quadruplication (if that is a word!)
That Millenium Bug didn't happen as feared, because companies whose operations depended on their computers NOT getting their knickers in a twist over date being exact took the precaution of getting their software checked line by line searching that 31/11/99 had been changed everywhere to 31/11/1999, and would be followed by 01/01/2001, not 01/01/00. DH had eighteen months of work prior to 2000 doing just that for a major company.
Chaos would indeed had happened, as among other things the automatic supplies of water, gas and electricity would have shut down, and the bills of their customers been either astronomical or non-existent.
Because it didn't happen, there was a lot of jeering at the scaredy-cats who had prophecied doom, but it was much the same as an industrial accident not happening because a firm cheked and rechecked safety precautions and put right any faults. No-one jeers at them for their careful checking.
That wasn't a groundless panic. There was software still in common use which had been designed years before that, when computers had a timy amount of storage and working space which would not have coped with a hundred times the number of possible dates. It had not been expected that the software would still be in use.
And the date wasn't used just to put at the top of a bill - the programmes check that all is well with the computer by frequently comparing the exact time and date that the computer thinks it is and the same for what the programme thinks it is. If they find a discrepancy they shut down the computer with an error message. (Programming buffs may not approve of that explanation, but it'll do for us non-nerds)