Just this year I ran into the year 2038 limit in MariaDB where converting between Unix timestamps and ISO dates (don't remember the direction). By the time this happened, a new version was already out that had that limit lifted, but the version I ran still had it. Cannot have been more than two years old.

On the plus side, businesses and administrations work with dates in the future a lot (think contract life times, leases, maintenance schedules etc.), so hopefully that flushes out many of the bugs ahead of time.