Here in the United States, the Writers Guild of America -- who write a lot of the television shows -- are on strike, and have been for two months. As a result, a lot of TV shows are in reruns, and the networks are starting to move into "reality" television which doesn't need writers.
Anyway, zap2it.com, a web page with TV listings, currently has a banner ad reading: "WRITERS' STRIKE DAY -307: Find out how the Hollywood writers' strike will affect you." The strike actually started on November 5, 2007; this is day 58.
Apparently whoever wrote the code which automatically generates these banners didn't consider the possibility that the strike might run into 2008. And 308 days from today (the putative "Day 1" if the count increments by one each day) is November 4, not November 5... 2008 is a leap year! If I had to guess, I'd say that the code incorporates the fact that the strike started on the 309th day of the year... which is November 5 in an ordinary year, but November 4 in a leap year.
And do people remember how occasionally, around eight years ago, you'd see web sites referring to "19100" for 2000, "19101" for 2001, and so on, since the code which was automatically generating the dates hadn't been fixed for Y2K? This error reminds me of that, although there's no mathematical similarity. But they're both "stupid calendar tricks".
(While I'm on the topic of calendars, check out Claus Tondering's Calendar FAQ.)