title: convert local time to utc and add to utc datetime moment
body: <p>I have a user input where the user enters year, month and day and I create a date object</p>
  
  <pre><code>  let userDate = new Date(year, month, day)
  </code></pre>
  
  <p>and then from a user input where the user enters minutes and hours (into variables minutes and hours)</p>
  
  <p>I need to convert this date and time into UTC timestamp, using moment and I'm not sure about it. Can I just do</p>
  
  <pre><code>  let utcTimestamp = moment.utc(date.toISOString()).hour(hours).minutes(minutes);
  </code></pre>
  
  <p>For example: if a user enters a date of 13-Mar-2018 and time of 8:45 AM (in GMT timezone), then I could use the above line of code to get UTC timestamp as I can directly add hours and minutes to the date</p>
  
  <p>if a user enters a date of 13-Aug-2018 and time 8:45 (which is GMT +1, due to daylight savings time change) then with above line I might be creating a wrong date.</p>