Answer: Stay In Orbit Over New Year’s

When you’re in the business of launching extremely expensive spacecraft with highly trained and difficult to replace astronauts aboard, it pays to be cautious. Throughout the 1980s, 1990s, and the first part of the 2000s, NASA engineers were extremely cautious when it came to what they called YERO or, Year End Rollover, and planning space shuttle missions.

Because the software used by the ground control and shuttle systems had never been tested during a Year End Rollover, the moment the date switches from December 31 to January 1 of the next year, NASA scheduled all shuttle flights so that no shuttle would be launching, in orbit, or returning at the time of the date rollover.

In 2007, software updates, after rigorous testing, were shown to be stable across YERO events and the restriction on keeping shuttles grounded on New Year’s Eve were relaxed.