@tubetime I recently did some work on an ancient SCO server that a company was running their ENTIRE BUSINESS on! They had files in the log from at least 1998...
They had a Y2K 'fix' in their ancient software that deducted something like 25 years from the date, did the maths, then added the years back onto the result.
They want to keep on using it, but the S/W company told them that in 2025, it's just not going to work anymore!
Can't come a moment too soon!