Comparing dates in Javascript and timezones

Question

When comparing dates in Javascript using <, >, =, >= and <= is the timezone used in any way in the comparison? I am hoping that the timezone is ignored.

I think this question may help you: stackoverflow.com/questions/17545708/… — sanyooh
– sanyooh, Commented Oct 23, 2014 at 15:22
There is no timezone in JavaScript dates. So No, it won't be used in the comparisons. — Bergi
– Bergi, Commented Dec 3, 2014 at 11:57
The = operator you mention does not compare but assign. On the other hand, Date objects, the operator == is not working as expected. — Wolf
– Wolf, Commented Dec 3, 2014 at 12:28

Wolf · Accepted Answer · 2014-12-03 15:46:08Z

10

The timezone part of string representation of a timestamp is taken into account as you would expect, when you convert it into JavaScript Date object: the internal value is a simple scalar, normalized to UTC. So there is no need for special timezone handling when comparing Date objects:

var d1 = new Date(Date.parse("Mon, 25 Dec 1995 13:30:00 +0430"));
var d2 = new Date(Date.parse("Mon, 25 Dec 1995 13:30:00 GMT"));
print("d1:", d1);
print("d2:", d2);
if (d1<d2) {
    print("d1 is less then d2");
} else if (d1>d2) {
    print("d1 is greater then d2");
} else {
    print("d1 equals to d2");
}

which gives this output:

d1: Mon Dec 25 1995 09:00:00 GMT+0000
d2: Mon Dec 25 1995 13:30:00 GMT+0000
d1 is less then d2

[see online demo]

You'll most probably get into trouble if you compare string representations of time stamps.

edited Dec 3, 2014 at 15:46

answered Dec 3, 2014 at 11:53

Wolf

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2 Comments

Bergi Over a year ago

Notice that == doesn't work on Date objects as you would expect

Wolf Over a year ago

@Bergi Thanks for pointing me on that strange JS behaviour!

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