I remember y2K very well. I was in charge of all computing at a large chemical facility and we had plenty to do in the run up. For example the purchasing system needed major changes as all PO numbers started with a 2 digit year and the search algorithm could not find a single PO once it started with 00. (We have development and test systems for all our major systems so we could test quite easily to see where we had problems)
Of the process control systems running the plants only one had an issue and it was to do with trending historical data on the operator consoles. Nothing dangerous but a real PITA. I told the production manager that the vendor offered an upgrade to fix it for $75k, or we could set the clock back "x" years so that the days of the week lined up with 2000 - so what if the year was 1982. However he went for the fix and after many fruitless attempts by the vendor they couldn't get the new system to work and so we got our money back and changed the clocks on the consoles.
Come New Years Eve I had 3 folks on site to cover the warehouse systems, the control systems and the networks. I brought the alcohol-free champagne which we used to celebrate after nothing happened and we had a jolly old time walking around the control rooms etc.
On the following Monday folks discovered that phone messages were being auto-deleted as the phone system thought messages in 2000 were 99 years old
No big deal.
In March when the older, closed, PO's were archived in the annual cleanup
all closed PO's were deleted and had to be recovered from back-up tape (missed the search algorithm in
that particular program)
On a personal level I just withdrew an extra $400 ahead of time in case of a "run" on atm's by panick'ed people. I made no investment changes but made sure I had copies of the latest statements for all my accounts.