"2012-03-18Z" isn't a valid datetime; drop the "Z"
"00:00:00Z" isn't a valid datetime; drop the "Z"
Drop invalid "Z" from some more date values.
Drop some more invalid "Z"s in datetime year vals
Make <time> text content a valid datetime value.
Merge pull request #29 from sideshowbarker/datetime

Make "datetime" values valid HTML5.