I worked as a cto in a publicly traded bank in the USA. In the USA, the regulation was that all banks had to have 10% of all deposits in cash. For example, If you were a billion dollar bank, you had to have 100 million in cash available at all times.
Because of Y2K, there were deep concerns their would be a bank run, so all banks had to have 20% of deposits as cash. Enormous sums of cash.
On New Year’s Eve 1999, my wife and I were taken by federal authorities to a safe house, where we were heavily guarded. We knew in advance they were taking us, but we didn’t know where and when it happened our cell phones were taken from us. Around 4 am they said everything was ok, my wife and I opened some champagne and they drove us home.

Y2K is one of those stories we look back on and think what a silly old load of nonsense. Truth is, if it wasn’t for the countless hours of overtime people put in to making those outdated systems support the date change, it really would have been utter carnage. You saw how crazy things got when we started to run low on toilet paper for a few weeks.