How do I create a moment object with just the time and not the date?

Question

Here is what I am trying to do.

I want to have a moment object with timezone GMT @16:00.

If this time is in the past then +1d and if it is in the future it will be the same day.

How do I do this and how do I set the time to 16:00 after I create the object?

This doesn't work:

var day = moment('16:00','HH:mm').tz('GMT');

If I make a new moment object how do I set the time after?

var day = moment.tz('GMT');

There is nothing like this day.set(16:00, 'time of day'):

Is there?

--- edits:

How can I set the time of day after Ii create it? If I go moment().tz(GMT) then it will be the current time in that zone. How can I change the time of day after that?

Also, how can I change the date of that object?

---

I have a string with the time. I want to parse this and put it into my moment object that I made above. What's the best way to do it?

var time = "16:00";

var day = moment().tz('GMT');

How to set the day time from the string?

Solution

Neither moment.js nor JavaScript have a time-of-day type. You can fake it by using an arbitrary day (e.g. 1970/01/01) for all of your time-of-day objects.

moment("1970-01-01 16:00Z")

EDIT:

var time = "16:00"
var day = moment().tz('GMT');
var splitTime = time.split(/:/)
day.hours(time[0]).minutes(time[1]).seconds(0).milliseconds(0);

EDIT 2020:

var time = "16:00"
var day = moment().zone('GMT');
var splitTime = time.split(/:/)
day.hours(parseInt(splitTime[0])).minutes(parseInt(splitTime[1])).seconds(0).milliseconds(0);