Date conversion Local to UTC and UTC to Local in Node.js

If you have your date+time in a JavaScript Date object you can call its getUTCDate()method to get a new Date whose time zone is UTC.

If that is not what you have in mind please be more specific about what you mean by “it will change”.

You can try this:

function calculateTimestamp(date) {
    date = date.split('-');
    var year = date[2];
    var month = date[1];
    var day = date[0];
    var d1 = new Date(Date.UTC(2017, 9, 1, 17, 0, 0, 0)); //It is static time based upon you will count time in ms
    var d2 = new Date(Date.UTC(year, (month - 1), day, 17, 0, 0, 0));
    return parseInt((d2.getTime() - d1.getTime()) / 1000);
}

var startDate = '27-02-2018';
var startTime = calculateTimestamp(startDate);

Now you can convert this timestamp again as below:

var d = new Date(Date.UTC(2017, 9, 1, 17, 0, 0, 0));
var t = parseInt(d.getTime() / 1000);

var d = new Date((startTime + t) * 1000);