A valid time string, such as "10:55", is one of the possible values for a valid date or time string:
http://www.whatwg.org/html5#vaguer-moments-in-time But step 10 of the parsing rules says: If the 'time present' flag is true, but 'position' is beyond the end of 'input', then fail. That would appear to fail on "10:55". I think making step 10 begin "If the 'date present' and 'time present' flags are both true" (as step 11 already does) fixes this. Smylers
