Caesar might have been warned, "Beware the Ides of March," but our modern day hero might've heard "Beware the Nines of September." Far less fanfare than our other favorite topic of Y2K, the 9999 day has been revered by some as a mystical event. Others have mentioned this date as a mark for potential destruction of files or inability for some computers to start because in some programming languages 9999 means "end of file." Programmers also have used 9-9-99 as shorthand for "never expires."
If you think that's wacky, thank the stars you didn't live in 1582, when Pope Gregory eliminated 10 days from the calendar that year. Imagine computer systems around the world dealing with Monday, October 5, 1582 and then Tuesday, October 15, 1582. This was a one-time remedy to address the fact that the spring equinox was occurring earlier than it should according to church calendars. (This information was garnered from http://earthsky.worldofscience.com/1999/esmi990315.html) As if life isn't spinning by uncontrollably as it is, we need some Pope to whisk away 10 days. If he could've just put them all into vacation time!