i\'m using moment.js with timezones for date manipulation in a webapp. i\'m storing all the dates in UTC and return them to UI as UTC. I\'m having the timezone of the user.
You can try:
moment.utc(utcDate).tz(timezone).format()
But it shouldn't matter. They should both produce: "2013-10-16T06:31:59-04:00".
It works for me, running on Chrome 30, so it's probably browser related.
If you're running Moment.js 2.3.1 or earlier on IE8, then it's a side effect of issue #1175, which was fixed in 2.4.0. Updating to the latest version should solve the problem.