On the last day of 2008 – a leap year – some models of the Zune were reported as not working. When the date rolled over to January 1, 2009, all was fine. Even though I was not impacted by this bug, I can relate.

At my second job out of college, our product was hit by a similar bug. The product used both Gregorian and Julian calendars (I do not recall why…). We had done all of the normal leap year tests around February 29 for the year in question. On New Years Eve and New Years Day, our support lines lit up. Some month end, quarter end and year end processes were failing. Sure enough, they did not expect 366 days in this year.

Ever since that time, I always wanted to have a set of systems that were running some number of months in the future so I could discover these misses before our customers did.