There is a claim circulating on Facebook that space shuttles couldn't fly near the end of the year because its onboard computers could not handle a year turnover.
Searching for the claim, I found Y2K-like fears create shuttle scheduling crunch, which says,
The space shuttle's computer software is about 30 years old and does not recognise when the calendar year switches. On 1 January 2007, for example, it will think it is day 366 of 2006 - a problem NASA calls 'year-end rollover'.
To reset the time, the shuttle's main computers would have to be 'reinitialised', which would mean a period without navigation updates or vehicle control, a situation NASA obviously wants to avoid.
As a programmer I know I should always store time as a Unix timestamp or some other T+x time representation, so I don't need to deal with timezones or other stuff. I only need to convert to or from actual date and time when presenting it or when parsing user input.
So I cannot believe NASA made such a mistake in that critical software.