That's what Google says, which I thought was based on a "clever look" at Last-Modified or explicit dates in the article. However, the articles mentions Windows

That's what Google says, which I thought was based on a "clever look" at Last-Modified or explicit dates in the article. However, the articles mentions Windows XP, which I think wasn't known until 2001. So Google might have just picked the only parseable date from the page. Edit: After about 5 minutes curl answered: Last-Modified: Mon, 27 Dec 2010 20:40:54 GMT (which is unsurprising given the web.archive.org info showing amends of the page)