Add "0" to countdown timer after it reaches 0

So basicly what I would like to do is have my countdown timer add a "0" once it reaches below "10". So far I have tried an if statement (In code below) which did not work. Here is my full code:

CountDownTimer('01/1/2017 12:0 AM', 'countdown');
  CountDownTimer('01/1/2017 12:0 AM', 'newcountdown');

  function CountDownTimer(dt, id)
  {
      var end = new Date(dt);
      var _second = 1000;
      var _minute = _second * 60;
      var _hour = _minute * 60;
      var _day = _hour * 24;
      var timer;

      function showRemaining() {
          var now = new Date();
          var distance = end - now;
          if (distance < 0) {
              clearInterval(timer);
              document.getElementById(id).innerHTML = 'EXPIRED!';
              return;
          }
          var days = Math.floor(distance / _day);
          var hours = Math.floor((distance % _day) / _hour);
          var minutes = Math.floor((distance % _hour) / _minute);
          var seconds = Math.floor((distance % _minute) / _second);

          // THIS IS THE "IF" STATEMENT THAT DID NOT WORK, EVERYTHING ELSE IS WORKING
          if (seconds < 10) {
            document.getElementById(id).innerHTML += '0' + seconds + '.';
          }

          document.getElementById(id).innerHTML = days + '.&nbsp;&nbsp;&nbsp;';
          document.getElementById(id).innerHTML += hours + '.&nbsp;&nbsp;&nbsp;';
          document.getElementById(id).innerHTML += minutes + '.&nbsp;&nbsp;&nbsp;';
          document.getElementById(id).innerHTML += seconds + '.';
      }

      timer = setInterval(showRemaining, 1000);
  }