Bugzilla – Bug 763
ins and del datetime attribute may take only a date (no longer require time)
Last modified: 2010-12-03 11:08:19 CET
The ins and del elements' datetime attribute is now a valid date string with **optional** time. (emphasis added). http://dev.w3.org/html5/spec/edits.html#attr-mod-datetime This was changed in the spec as of August 24th http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2010-August/028113.html as the spec used to require a date and time in the ins and del elements' datetime attribute.
https://github.com/validator/syntax/commit/5e16871
Thanks for the bug report. This is now fixed in the sources, though not yet deployed at validator.nu -- but in the mean time you can test it here: http://www.w3.org/html/check
https://bitbucket.org/validator/syntax/changeset/316901c3edb3