3/16/2007

The <lastmod> tag specifies the time that the corresponding Sitemap file was last modified. A lot of people make the mistake of thinking the <lastmod> tag relates to the modified date of the web page, this is not true.

The idea behind <lastmod> is to allow large web sites to inform the web crawlers which parts of their sitemaps have changed.

Although, you can rest assured that even if the <lastmod> value is incorrect it will have little effect on the web crawlers anway.