 <p>Call <code>moment.utc()</code> the same way you're calling <code>Date.UTC</code>: </p> <pre><code>var withMoment = moment.utc([now.getFullYear(), now.getMonth(), now.getDate(), now.getHours(), now.getMinutes(), now.getSeconds()]).valueOf(); </code></pre> <p>I think calling <code>moment.utc(now)</code> will make it assume <code>now</code> lives in the local timezone, and it will convert it to UTC first, hence the difference.</p>