Why subsract Date Objects doesn't works

Question

I have that function:

function CompareDate() {
    var timeNow = '03.04.2019';
    var timeNowSplit = timeNow.split('.');
    var timeTarget = '04.04.2019';
    var timeTargetSplit = timeTarget.split('.');

    var timeNowObj = new Date(timeNowSplit[2], timeNowSplit[1], timeNowSplit[0]).toUTCString();
    var timeTargetObj = new Date(timeTargetSplit[2], timeTargetSplit[1], timeTargetSplit[0]).toUTCString();

    difference = timeTargetObj - timeNowObj;
    console.log(difference)
}

If i'm launching this inside a node.js console i'm getting just:

"C:\Program Files\nodejs\node.exe" C:\Users\s.manns.WebStorm2018.3\config\scratches\scratch.js NaN

That solution i found on How to calculate date difference in javascript

But why this code just returns a "NaN"?

Remove the `.toUTCString()` bit from both and just subtract the date objects — adiga, Apr 03 '19 at 09:41
...and Month is `monthIndex` - Integer value representing the month, beginning with `0` for January to `11` for December. :) — Eddie, Apr 03 '19 at 09:42

DKyleo · Accepted Answer · 2019-04-03T09:48:00.900

The reason is because you are attempting to calculate the difference of two strings. Remove the toUTCString() from both and it will result in a valid response. For completeness, please note the response you receive will be in milliseconds!

var timeNow = '03.04.2019';
    var timeNowSplit = timeNow.split('.');
    var timeTarget = '04.04.2019';
    var timeTargetSplit = timeTarget.split('.');

    var timeNowObj = new Date(timeNowSplit[2], timeNowSplit[1]-1, timeNowSplit[0]);
    var timeTargetObj = new Date(timeTargetSplit[2], timeTargetSplit[1]-1, timeTargetSplit[0]);

    difference = timeTargetObj - timeNowObj;
    console.log(difference);

score 0 · Answer 2 · answered Apr 03 '19 at 09:43

0

The method you are using Data.prototype.toUTCString() which changes the date object to UTC equivalent string. Try removing the method and then subtract.

answered Apr 03 '19 at 09:43

Pranay Tripathi

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score 0 · Answer 3 · answered Apr 03 '19 at 09:46

This should work for you -

function CompareDate() {
    var timeNow = '03.04.2019';
    var timeNowSplit = timeNow.split('.');
    var timeTarget = '04.04.2019';
    var timeTargetSplit = timeTarget.split('.');

    var timeNowObj = new Date(timeNowSplit[2], timeNowSplit[1], timeNowSplit[0]);
    var timeTargetObj = new Date(timeTargetSplit[2], timeTargetSplit[1], timeTargetSplit[0]);

    difference = timeTargetObj - timeNowObj;
    console.log(difference)
}
CompareDate();

Why subsract Date Objects doesn't works

3 Answers3