Guessing here: it might be a unit test which only works during the current year. I came back to work from holidays in January 2011 to exactly that. Someone had

Guessing here: it might be a unit test which only works during the current year. I came back to work from holidays in January 2011 to exactly that. Someone had coded a test for "August 15th" being a certain day of the week. It worked great until the year changed. That particular test hung out unnoticed for at least 4 months. Its failure was inevitable.