Well, I looked at a Year 10000 problem less than 2 hours ago. We're parsing logs to extract the timestamp and for that, we're using a regex which starts with:
\d{4}-\d{2}-\d{2}
So, we assume there to be 4 digits for the year, always. Can't use it, if you live in the year 10000 and beyond, nor in the year 999 and before.