CODEWITHSUNDEEP
javascriptarraysdate
Ben Taliadoros
Ben Taliadoros

Reputation: 9371

Why does the JS date act like this?

I have an array called dateArr which contains: [2014, 07, 10];

When I create a date out of it like below:

new Date(dateArr[0], Number(dateArr[1]), Number(dateArr[2]), 0, 0, 0);

It evaluates to '2014-08-09T23:00:00.000Z' in the console. I understand thats months are zero based, but why, to correct the time, do I have to do this:

new Date(dateArr[0], Number(dateArr[1]) - 1, Number(dateArr[2]), 1, 0, 0);

Which gives: 2014-07-10T00:00:00.000Z

This doesn't seem right to me, could someone explain?

Upvotes: 0

Views: 74

Answers (2)

Alexey Ten
Alexey Ten

Reputation: 14354

new Date(2014, 6, 10, 0, 0, 0) uses your current timezone (which is +0100 for you, and, e.g. +0400 for me in Moscow). So it's result will depends on timezone where you run the code.

> new Date(2014, 6, 10)
Thu Jul 10 2014 00:00:00 GMT+0400 (MSK)
> new Date(2014, 6, 10).toISOString()
'2014-07-09T20:00:00.000Z'

if you really want midnight in «ISO time» you could use constructor with string:

> new Date('2014-06-10Z').toISOString()
'2014-06-10T00:00:00.000Z'

Upvotes: 2

Daniel
Daniel

Reputation: 3514

Your tools are working with different timezones. (chrome dev tools output indicates that by adding GMT+0100(BST) to your output and therefore converting it to BST (British summer time) While webstorm gives you a utc/gmt time. In fact 2014-07-09T23:00:00.000 is exactly the same time as Thu Jul 10 2014 00:00:00 GMT+0100 (BST).

You may use Date.UTC() to generate a correct timestamp (but this will then be one hour off into the other direction in your local time)

I tried that within my own chrome developer console:

> new Date(Date.UTC(2014, 6, 10, 0, 0, 0))
Thu Jul 10 2014 02:00:00 GMT+0200 (MESZ) //middle european summer time

Upvotes: 1

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