I thought iPhoto 3 and 4 had an odd Y2K bug because no matter how often I set an early picture's date to 1917, iPhoto insisted on sorting as if the date was 2017. Turns out the sort is controlled by the System's "Short Date" setting -- turning on "Show Century" in System Preferences -> International -> Date fixed the problem.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040503131731286