Seems the most foolproof way to start with a UTC date is to create a new Date object and use the setUTC… methods to set it to the date/time you want.

Then the various toLocale…String methods will provide localized output.

Example:

// This would come from the server.
// Also, this whole block could probably be made into an mktime function.
// All very bare here for quick grasping.
d = new Date();
d.setUTCFullYear(2004);
d.setUTCMonth(1);
d.setUTCDate(29);
d.setUTCHours(2);
d.setUTCMinutes(45);
d.setUTCSeconds(26);

console.log(d);                        // -> Sat Feb 28 2004 23:45:26 GMT-0300 (BRT)
console.log(d.toLocaleString());       // -> Sat Feb 28 23:45:26 2004
console.log(d.toLocaleDateString());   // -> 02/28/2004
console.log(d.toLocaleTimeString());   // -> 23:45:26

Some references:

• toLocaleString
• toLocaleDateString
• toLocaleTimeString
• getTimezoneOffset

You might want to check out 10 ways to format time and date using javascript.

You can do something like this, for example, for each of the dates:

var example_date = '2017-09-14T22:11:05.5303556';

function formatDate(date) {
	var d = new Date(date),
		month = d.getMonth(),
		date = d.getDate(),
		year = d.getFullYear(),
		hours = ('0' + d.getHours()).slice(-2),
		minutes = ('0' + d.getMinutes()).slice(-2),
		seconds = ('0' + d.getSeconds()).slice(-2);

    month++;

    return (month + '/' + date +'/' + year + ' ' + hours + ':' + minutes + ':' + seconds);
}

console.log(formatDate(example_date));

You could also make use of .toLocaleTimeString() and .toLocaleDateString() and combine the two.

If you're not averse to using a 3rd party library, I'd recommend taking a gander at MomentJS. It's very good at allowing you to easily format date/time, e.g...

for (var i in json){
  json[i].dateCreated = moment(json[i].dateCreated).format('MM/DD/YYYY hh/mm/ss');
}

...where json is the object returned, would produce:

[{"id":98,"dateCreated":"09/14/2017 10/11/05"},{"id":99,"dateCreated":"09/14/2017 10/11/05"}]

Per my test and search, it seems the toLocaleDateString() cannot convert date format. We can do it manually with an expression like this:

=getYear(@currentField)+'-'+(getMonth(@currentField)+1)+'-'+getDate(@currentField)

Just as OP mentioned, the getMonth returns a 0-based value, we need to add 1 for it.

getMonth: returns the month in the specified date according to local time, as a zero-based value (where zero indicates the first month of the year). - Only available in SharePoint Online