Send ISO 8601 date for content#create actions.

MOTIVATION & SCOPE : Closes #1143
TESTING : Check Travis CI and pull down code to check.
REVIEWERS : @zr2d2, @simplysoft, @bamnet
I think you actually want to knock out the else clause below this if instead of the if Hash logic.  If hash, elseif string.  _start_time will either be a hash (if someone has built their own completely custom content form) or a string (if they are using your updated JS logic like they should)... there's no more else scenario for a non-string non-hash.