date-picker.js

    function bindRange(scope, el, attrs){
      var getFrom = $parse(attrs.pickFrom);
      var setFrom = getFrom.assign;
      var getTo = $parse(attrs.pickTo);
      var setTo = getTo.assign;
      var time = hasTime(attrs);

      function updateField(){
        var from = getFrom(scope);
        var to = getTo(scope);

        el.val(dateParsing[time ? "formatRangeWithTime" : "formatRange"](from, to));
      }

      scope.$watch(getFrom, updateField);
      scope.$watch(getTo, updateField);

      el.on('keyup', function(){
        var parseMethod = time ? "parseRangeWithTime" : "parseRange";
        var parsed = dateParsing[parseMethod](getFrom(scope), getTo(scope), el.val());

        setFrom(scope, parsed.from);
        setTo(scope, parsed.to);
      });
    }