Datetime fields with client_side_validations gem

_form.html.haml

form_for(@user, :validate=>true) do |f|
      = f.label :birthdate
      = f.date_select :birthdate
      = f.text_field :birthdate, :type=>"hidden", 'data-validate'=>true
end

application.js

$('select[id^=user_birthdate]').live('blur', function() {
    setTimeout(function() {
        if ($('select[id^=user_birthdate]:focus').length == 0) {
            // update the hidden date
            var curYear = $('#user_birthdate_1i').val(),
                    curMonth = $('#user_birthdate_2i').val(),
                    curDay = $('#user_birthdate_3i').val();

            hiddenDate = "";
            if ((curYear * curMonth * curDay) != 0) {
              hiddenDate = curMonth + "-" + curDay + "-" + curYear;
            }
            var elem = $('input[id=user_birthdate]')
            elem.val(hiddenDate);
            elem.data('changed', true); // tells validator it changed
            elem.trigger('focusout');   // manually trigger focus out
        }
    }, 20);
});