title: Moment js not adding hours and minutes to a specific time
body: <p>I have a start time to which i would like to add an end time to.
  for example</p>
  <pre><code>startTime=19:09
  endTime=00:51 // 0 hours and 51 minutes
  </code></pre>
  <p>i want to add the 51 minutes to the 19:09 to make it 20:00.</p>
  <p>I have tried multiple different scenarios as showing bellow but nothing is giving me the correct time</p>
  <p>i tried</p>
  <pre><code>let [hour, minute] = endTime.split(':').map(Number);
  this.endTime = Moment(startTime)).add({ hour: 'hours', minute: 'minutes' }) // also tried .add(hour,'hours').add(minute,'minutes')
  </code></pre>
  <p>which still outputs 19:09. its just ignoring my end time</p>
  <p>i tried</p>
  <pre><code>Moment(endTime, 'hh:mm').add(Moment.duration(startTime)).format(&quot;hh:mm&quot;);
  </code></pre>
  <p>which gives me an output of 08:00 when it should be 20:00</p>
  <p>What am i doing wrong?
  i want to add the end time to a start time.
  Keep in mind that my endTime is always changing so sometimes it could be 13:05 etc cause its a user input</p>