As stated by Gautam, it is important to take into consideration what timezone has been set in the regional settings of your SP site.
As per my understanding, if the SP timezone is set as 'America/Los_Angeles' then at the time of saving the item SharePoint will convert the date time you entered in ISO string format like this "2017-12-06T19:00:00Z" and save it.
While displaying the date time in any list view, SharePoint will automatically convert the ISO string to the timezone set in regional settings ("12/6/2017 11:00 AM" in this case).
Hence to summarize if you want to show the ISO String to user in agreement with what is being displayed in list view, simply convert the ISO string to the timezone set in your site's regional settings.
With the help of moment library it can be done fairly easily as shown below:
var itemDate = moment('2017-12-06T19:00:00Z')
console.log(moment.tz(itemDate,'America/Los_Angeles').format('MM-DD-YYYY HH:MM:SS Z'));
//outputs 12-06-2017 11:00:00 -08:00
https://site-coll-url/_layouts/15/regionalsetng.aspx
) and check if they are correct. If not, update it to the correct time zone and then run the code.