Somewhat related, but I've seen a lot of retry-with-a-timeout loops that will either throw a spurious timeout error or wait for a very long time if the system clock just happens to jump at the right time.
Another amusing anecdote: I got an old PowerBook out of storage and booted it up. The battery had run flat, so the clock reset to 1970. Spotlight noticed this and decided it had to reindex the entire drive. At some point during all of this, NTP kicked in and reset the clock to the correct year. I wanted to see how long Spotlight would take to finish indexing, so I popped down the menu. The progress bar indicated that it was about halfway done, and based on how long it had taken so far, it estimated that only another 40 years would be required to finish!
Another amusing anecdote: I got an old PowerBook out of storage and booted it up. The battery had run flat, so the clock reset to 1970. Spotlight noticed this and decided it had to reindex the entire drive. At some point during all of this, NTP kicked in and reset the clock to the correct year. I wanted to see how long Spotlight would take to finish indexing, so I popped down the menu. The progress bar indicated that it was about halfway done, and based on how long it had taken so far, it estimated that only another 40 years would be required to finish!