I just added a feed for my own site in my RSS reader. The RSS header shows:
News and Opinion - Canada and the World
PubDate: Tue, 16 May 2005 08:51:26 -0700
Everything is correct, except that May 16 should be Mon--not Tue.
I contacted the author of my RSS reader (NewzCrawler) and he says that he simply displays the PubDate parameter exactly as it specified within the feed source without any modifications.