The Zune was Microsoft's portable music player. The Zune 30GB was its 2006 model, and by the end of 2008, Microsoft said, "a large number" were still in use.
At midnight Pacific time on 31 December 2008, Zune 30GB players began to freeze, The Register reported. Owners woke up on New Year's Eve to players that were frozen solid.
2008 was a leap year, so 31 December was its 366th day. Microsoft's explanation: "a bug in the internal clock driver related to the way the device handles a leap year". In other words, the last day of a leap year: a day that comes around only once every four years.
Microsoft's fix was not a software update. Its support page gave instructions instead:
- Disconnect the Zune from USB and power, and let the battery run flat. Microsoft called that drain "good"; on a full battery it "might take a couple of hours".
- Wait until after noon GMT on 1 January 2009 (7 a.m. Eastern, 4 a.m. Pacific).
- Charge it. "No other action is required".
A Zune still working that day was fine, the page said, as long as its owner didn't connect it to a computer before noon GMT on 1 January. Plugging it in would freeze it too, "even if that computer does not have the Zune software installed". And no, opening it up to pull the battery was "a bad idea", one that would void the warranty.
Once the calendar had moved on to 1 January and the battery had some charge, the player "should start normally".
- 366 days in 2008; the freeze came on day 366
- 30GB: the 2006 model Microsoft named
- Noon GMT, 1 January 2009: when it was safe to charge again
- About 24 hours: how long Microsoft said the issue would take to clear itself
Why it matters: Dates have edge cases that come around rarely: leap days, the 366th day, the end of a month. Test them on purpose, by setting the clock forward, because waiting four years is not a test plan.