When your day ends with something VERY unexpected. This event doesn't have to be tragic, but it can be.
Named for the fact that a large portion of Kevin Spacey's movies have a surprise ending, such as Se7en, KPAX, American Beauty, The Usual Suspects, and Pay it Forward.
I took my girlfriend to a nice picnic in the park at sunset, followed by a late movie, then we went back to my place and made love for hours. I awoke to a breakup letter lying on the pillow. What a Spacey Ending!