As I type this, I'm looking at a boatload of July 4th-specific ads on some of my AdSense sites. It's currently July 17th by my watch. Since AdWords allows you to very easily set a stop date for campaigns, I don't really understand why I'm still seeing this, but once again I post this as a reminder to all. If you have time or date specific campaigns, pay attention and make sure they're either updated or stopped when the date has past. I sometimes see ads for things like wine tasting events from three months past. It's lose-lose; if people don't click, the publisher (or Google) loses out, and if people do click, the advertiser loses out.
I'm not immune; last year I found a bunch of ads buried deep in a campaign that mentioned the year 2006 (!)