Why I'm getting a false date

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I would like to convert a given date from dd.mm.yyyy to yyyy-mm-dd. I tried the Code below. But if i'm giving a "22.10.2018" the script Returns "2018-11-21T23:00:00.000Z". But why?

What I have tried:

function hasError() {
    function toDate(datestr) {
        var parts = datestr.split(".")
        return new Date(parts[2], parts[1], parts[0])
    }

    var comparestart = toDate("22.10.2018");
    var compareende = toDate("02.11.2018");   

    console.log(comparestart);
    console.log(compareende);

    if(comparestart >= compareende) {
        console.log(true);
    } else {
        console.log(false);
    }
}

hasError();

Posted 19-Oct-18 2:11am

Sascha Manns

Updated 19-Oct-18 10:58am

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Comments

F-ES Sitecore 19-Oct-18 8:17am

comparestart etc are dates and you're asking a date to represent itself as a string, so it shows itself in its default format. If you want your date in a specific format then you'll have to write a function that outputs the various date parts in the desired format, or use a library that has these functions already.

If you google "javascript format date" you'll find many many examples of how to format dates.

Richard MacCutchan 19-Oct-18 9:08am

Probably because the date has been adjusted to the locale's timezone.

Richard MacCutchan 19-Oct-18 9:32am

Of course; thank you for reminding me.

3 solutions

Solution 2

Hello, thank you very much for all your help. Finally i used that Code:

function hasError() {
    function toDate(datestr) {
        var parts = datestr.split(".")
        return new Date(parts[2], parts[1] -1, parts[0]).toLocaleString('de-DE', {timeZone: 'Europe/Berlin'})
    }

    var comparestart = toDate("$Start");
    var compareende = toDate("$Ende");

    if(comparestart >= compareende) {
        return true;
    } else {
        return false;
    }
}

Because it will just executed by our german customers, that could be acceptable.

Thank you all again.

Posted 19-Oct-18 4:25am

Sascha Manns

Solution 3

Warning: Solution 2 can result in a wrong date. The code: new Date(...) still uses your local machine timezone.

For instance, if you run this code in California you'd get: 2018-10-19 00:00:00 GMT-8 -> 2018-10-19 10:00:00 in Germany (same day).

But if you run this code in Beijing, China, you'd get: 2018-10-19 00:00:00 GMT+8 -> 2018-10-18 18:00:00 in Germany. The previous day!

If you want to get rid of timezone issues, I'd recommend you to always use UTC. For instance:

function toDate(datestr) {
    var parts = datestr.split(".");
    return new Date(Date.UTC(parts[2], parts[1] -1, parts[0]));
}


var comparestart = toDate("$Start");
var compareende = toDate("$Ende");

if (comparestart >= compareende) {
    return true;
} else {
    return false;
}

To display the date you can use any of the following:

date.toUTCString()
date.toLocaleString('de-DE', {timeZone: 'UTC'})
date.getUTCDate() + '.' + (date.getUTCMonth() + 1) + '.' + date.getUTCFullYear()

Posted 19-Oct-18 10:58am

Gabriel 2

Updated 19-Oct-18 11:05am

v2

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Gabriel 2 · Accepted Answer · 2018-10-19T03:42:00

There are 2 issues with the code:
1 - "Date" object asumes month number to start in 0, not 1. The line:

new Date(parts[2], parts[1], parts[0])

should be:

new Date(parts[2], parts[1] - 1, parts[0])

2 - Notice "new Date" asumes hour to be in your local timezone (also affected by daylight saving). In this case, new Date(year, month-1, day) creates a date in your local 00:00:00 time. Which of course would be a different local hour for any other timezone. Any location on the west to you would be the previous date.

To avoid timezone issues, use always UTC functions. Eg:

new Date(Date.UTC(parts[2], parts[1] - 1, parts[0]))