Because my sister and a friend wanted to blog in Dutch, I've written locale handling for pyblosxom.
It's disabled by default, but once it's enabled, "date-style" URL's (http://your.blog/2006/May) will only work in the set locale (http://your.blog/2006/mei if your locale is Dutch, for example). It takes care not to break "standard" time/date formats (W3C, RFC2822), too. Most plugins I've tried also work with it out of the box.
If a plugin doesn't work, please report it to me, so I can send the author a patch. Usually it's an easy fix (don't use static names for months, etc.).
Op dit werk is een Creative Commons Licentie van toepassing.