My XML sitemap file has <lastmod>2013-07-06T09:39:51-0400</lastmod> formatted with W3C Datetime Format. Google has a warning message in webmaster tools about this for me:

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Google's help document about error sitemap errors states:

This could be because a date is in the incorrect format, or the date itself is not valid. Dates must use W3C Datetime encoding, although you can omit the time portion if you wish. For example:

  • 2005-02-21
  • 2005-02-21T18:00:15+00:00

2 Answers 2



The W3C datetime format includes a : (colon) in the time zone offset, separating the hours and minutes. So the last bit should read: -04:00.


just make sure there will be no space in between a single space will give invalid date or something error like that. for example

  • 2005-02-21T18:00:15 +00:00 -- space in between
  • 2005-02-21T18:00:15+00:00 -- no spaces here valid markup

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