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
2005-02-21T18:00:15 +00:00-- space in between2005-02-21T18:00:15+00:00-- no spaces here valid markup