When submitting a SEO Toolkit generated sitemap to google, I get a warning about the lastmod tag invalid date
looking at the w3c specs:
YYYY (eg 1997)
YYYY-MM (eg 1997-07)
YYYY-MM-DD (eg 1997-07-16)
YYYY-MM-DDThh:mmTZD (eg 1997-07-16T19:20+01:00)
YYYY-MM-DDThh:mm:ssTZD (eg 1997-07-16T19:20:30+01:00)
YYYY-MM-DDThh:mm:ss.sTZD (eg 1997-07-16T19:20:30.45+01:00)
these are the possible combo's
SEO toolkit does: 2009-06-07T15:54:34 and is missing TZS= time zone designator (Z or +hh:mm or -hh:mm)
So pretty much a extra Z in the end would fix this.
</lastmod>