How to manipulate date in JavaScript

Question

I'm having problem with manipulation of dates. I have a variable savedTime variable in localstorage which contains this date:

Wed Aug 31 2016 16:31:30 GMT-0300 (Hora oficial do Brasil)

I need add 1 hour for this variable savedTime to check if passed 1 hour:

var savedTime = new Date(savedTime); //converts string to date object
var checkExpired = savedTime.setHours(savedTime.getHours() + 1); //add 1 hour to savedTime

But on trying add 1 hour to this variable converting the string in a object, this (savedTime) returns:

1472675490000

What I expected is the string with + 1 hour:

Wed Aug 31 2016 17:31:30 GMT-0300 (Hora oficial do Brasil)

And compare dates to check if passed 1 hour

var currentDate = new Date();
if(currentDate > checkExpired) {
    //passed 1 hour
}

Do you want to be able to compare the dates or be able to format the number you got from the date? — Niles Tanner
– Niles Tanner, Commented Aug 31, 2016 at 20:59
You seem to be getting exactly what you want, but dates in javascript are in milliseconds, only the string representation is in the expected format ? — adeneo
– adeneo, Commented Aug 31, 2016 at 21:01
You are comparing 1472675490000 with 26 Wed Aug 31 2016 22:01:11 GMT+0100 (BST) which cant be compared to be greater than — Paul Fitzgerald
– Paul Fitzgerald, Commented Aug 31, 2016 at 21:01

C14L · Accepted Answer · 2016-08-31 21:02:49Z

5

instance.setHours() manipulates the instance. So you can do

d = new Date('Wed Aug 31 2016 16:31:30 GMT-0300');
d.setHours(d.getHours() + 1);

Now d contains the new datetime.

answered Aug 31, 2016 at 21:02

C14L

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Comments

noggin182 · Accepted Answer · 2016-08-31 21:09:54Z

2

setHours will manipulate the current object and return it's new value. Instead of using the return value, just continue to use the object.

var savedTime = new Date(savedTime); //converts string to date object
savedTime.setHours(savedTime.getHours() + 1); //add 1 hour to the savedTime

if (currentDate > savedTime) {
    //passed 1 hour
}

answered Aug 31, 2016 at 21:09

noggin182

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Comments

guest271314 · Accepted Answer · 2016-08-31 21:02:07Z

0

Use .getTime()

if(currentDate.getTime() > checkExpired) {
    //passed 1 hour
}

answered Aug 31, 2016 at 21:02

guest271314

1

Comments

AlexanderGriffin · Accepted Answer · 2016-08-31 21:00:18Z

0

You are getting the value back in milliseconds from the 'epoch date' which is January first 1970.

If you want this in the correct format, you will need to parse this information out into that with some math / other Date object functions.

Here is the documentation to do that, it's very straightforward:

JS Date Formatting

answered Aug 31, 2016 at 21:00

AlexanderGriffin

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