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Incorrect timezone adjustment in moment.js and spacetime

My server is sending my Javascript client a timestamp in UTC. I'm currently in Mountain Time which is currently in daylight savings (GMT-7), but any timezone adjustment I do is only applying -6 offset.
To confirm that javascript is even aware of my timezone, I did the following:
console.log(Date().toString()); which outputs the following: Mon Nov 19 2018 12:13:28 GMT-0700 (Mountain Standard Time). It's clear that JS knows I am currently in GMT-7.
Now, my server is sending 2018-08-24T17:00:00. So I parse it with moment.js, convert to local timezone and then format the result.
moment.utc(this.props.value).local().format('h:mm A')
The resulting value is 11:00 AM. 17:00:00 - 7 offset is 10:00 which is 10:00 AM. Why is javascript converting into 11:00? I get the same result if I try the spacetime library:
const s = spacetime(this.props.value,'UTC')
s.goto(spacetime().timezone().name);
console.log(s.format('h:mm a')); // Also spits out 11:00 AM
If I manually adjust the moment object with the offset, it works correctly:
var m = moment.utc(this.props.value);
m.add(-(new Date()).getTimezoneOffset(), 'minutes');
console.log(m.format('h:mm A')) // Outputs the correct time: 10:00 AM
Why is moment and spacetime both not adjusting my timezone correctly when Javascript is clearly aware of what timezone I'm in? The same problem occurs in both Chrome and Microsoft Edge. For now I will use the hacky workaround above, but I'd prefer to use the native methods so I'm curious as to why this isn't working. Any ideas?

Mountain Standard Time is UTC-7
Mountain Daylight Time is UTC-6
It is currently November 19th, and DST is not in effect, so you currently get UTC-7
For the date you gave, 2018-08-24T17:00:00, DST is in effect, so you get UTC-6
Everything is working correctly.
In other words, it doesn't matter whether it is currently in effect or not, only whether it is/was/will be in effect for the date in question.
Regarding this part:
m.add(-(new Date()).getTimezoneOffset(), 'minutes');
Don't do that. You aren't adjusting the time zone, you're picking a different moment in time.

Why has the representation of time zone of Date.toString changed in Node/Chrome and how do I change it back?

It appears that between v8 and v10 of Node, and around a similar time in Chrome (currently reproduced in version 69.0.3497.100), the Date.toString method stopped returning the time zone portion of the output as an acronym and started returning it as whole words.
The Date.toString example at MDN indicates that
new Date('August 19, 1975 23:15:30').toString()
Should return an acronym in initials, like
Tue Aug 19 1975 23:15:30 GMT+0100 (BST)
Which I've confirmed works in Node 8. However, when I run the same code in Node v10, I receive this:
Tue Aug 19 1975 23:15:30 GMT+0100 (British Summer Time)
Without using any string code or manually making the initials from the words, is there a way to extract the initials of the current time zone?
Note that any solution should work in Node AND Chrome.

The solution should be to set the timeZoneName property of the options object to either "short" or "long" (MDN link) — but that’s just giving me GMT+1 for short:
> d = new Date
> d.toLocaleString('en-US',{timeZone:'America/Los_Angeles',timeZoneName:'long'})
'10/19/2018, 3:31:04 AM Pacific Daylight Time'
> d.toLocaleString('en-US',{timeZone:'America/Los_Angeles',timeZoneName:'short'})
'10/19/2018, 3:31:04 AM PDT'
> d.toLocaleString('en-US',{timeZone:'Europe/London',timeZoneName:'long'})
'10/19/2018, 11:31:04 AM British Summer Time'
> d.toLocaleString('en-US',{timeZone:'Europe/London',timeZoneName:'short'})
'10/19/2018, 11:31:04 AM GMT+1'
Firefox is also giving me GMT+1 for short and in addition GMT+01:00 for long.
If you reliably need zone names, look into Moment — see their section on abbreviated time zone names.

Start of Day from one timezone to GMT

I am using moment-timezone library to build a UI that needs to be relative to a variety of timezones.
I am taking an input of a timezone, i.e "America/Chicago" and need to get the start of day in GMT.
For instance, if today is March 27th at 9am Chicago time (2pm GMT), I need to get the date in epoch seconds for March 27th, 00:00 AM.
I'm using the moment.tz("America/Chicago").startOf('day') but I keep getting Tue Mar 27 2018 01:00:00 GMT-0400 (EDT) . Any idea how to do this?
Thanks

// This part you are already doing correctly.
// You get back a Moment object representing the start of the current day in Chicago:
var m = moment.tz("America/Chicago").startOf('day');
I need to get the date in epoch seconds
// Ok, so simply now get the associated Unix Time
var timestamp = m.unix();
Also note that the correct terminology is "Unix Time", not "epoch seconds".
See my blog post: "Please don't call it Epoch Time".
... but I keep getting Tue Mar 27 2018 01:00:00 GMT-0400 (EDT)
You are probably either looking at _d or a Date object, or rather the string representation of one. Don't. See this Moment.js documentation for details.
Per your comment:
I need to take the current time in a specific timezone. I then need to convert that time to the corresponding day in GMT. Finally I need to get the midnight epoch timestamp of that GMT day.
That's a little different then you originally asked, but it would be like this:
var timestamp = moment.utc().startOf('day').unix();
Note that there's no purpose in involving another time zone for this operation. Logically, when asking for "Now in time zone A converted to time zone B", it's the same as asking for "Now in time zone B". In other words, you would get the same value even when the time zone was present:
var timestamp = moment.tz('America/Chicago').utc().startOf('day').unix();
So you're better off just leaving the time zone out.

How do I change the time zone in JavaScript?

I've been working on a time app for JS and I was wondering, how could I change the time zone. See, I live in the eastern time zone of North America, and i don't like converting it to the International Timezone. So here is my Code.
<button type="button"
onclick="document.getElementById('time').innerHTML = Date()">
Click me to display Date and Time.</button>
<p id="time"></p>
When I click the button, I get,
Wed Dec 30 2015 13:40:25 GMT+0000 (UTC)
But I want it to be:
Wed Dec 30 2015 8:40:25 (EST)

Date.prototype.toString is supposed to give you a string in your local time (as configured on your client).
When you click Run code snippet this should show an alert dialog with your local time string (toString is implicitly called, like in your example);
alert(new Date());
If it does give you the expected result then either you client timezone is not configured correctly or the browser you are using is bugged.

Javascript date formatting - one hour out due to daylight saving

So now, its 9:23am. I have a UTC date string that represents the current date, that looks like this "2012-07-17T09:23:27.75"
I want that in a date object, so I can display a nicely formatted date, so I:
var myDate = new Date("2012-07-17T09:23:27.75")
// Gives --> Tue Jul 17 2012 10:23:27 GMT+0100 (GMT Daylight Time)
So because of daylight saving time I'm getting an hour-out issue. I can see that myDate.getTimezoneOffset() gives me -60, what's the standard / best practice way to get my date to actually reflect the current correct time? Have I just entered javascript date hell?

Try momentjs.com. I really found it handy for such things.
var myDate = moment("2012-07-17T09:23:27.75");
Gives you a date instance in your timezone (that basically configured on your computer). Moreover momentjs has nice human friendly formattings like "a couple of seconds ago", "a month ago",...
Dates are really a hell in JS (but not only in JS). The best thing you can do is to always only transport in UTC between browser <-> server. Then on the server convert it to what time format you like, you obviously only have to be consistent. That way I managed to handle date-times properly.

Try removing the 'T'
I was debugging some date time format issue in chrome when I found out that in console
new Date('2016-04-16T15:15:00') returns Sat Apr 16 2016 16:15:00 GMT+0100 (GMT Daylight Time)
while
new Date('2016-04-16 15:15:00') returns Sat Apr 16 2016 15:15:00 GMT+0100 (GMT Daylight Time)