Why am I getting this error for JavaScript Date object?

Question

I wrote the following code in JS

var d = new Date(2019, 9, 14);

var currentTime = d.getTime();
var daysToAdd = 3;

var secondsInDay = 86400;

var d = new Date(currentTime + daysToAdd*secondsInDay);

var year = d.getFullYear();
var month = ("0" + (d.getMonth())).slice(-2);
var day = ("0" + d.getDate()).slice(-2);

console.log('result in Y-M-D is: ' + year + '-' + month + '-' + day);

This outputs to result in Y-M-D is: 2019-09-14

What am I doing wrong here? How to I change this to output result in Y-M-D is: 2019-09-17 , which I originally intended to do

you need to add milliseconds.... daysToAdd*secondsInDay*1000 Check the details developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — gp.
– gp., Commented Oct 16, 2018 at 0:48
One other issue you will come up against ... you're setting new Date(2019, 9, 14) - this, as you know is actually, 14th October 2019 - however, the output string you want to create is 2019-09-17 - which would imply 17th September 2019 - perhaps not what you intended — Jaromanda X
– Jaromanda X, Commented Oct 16, 2018 at 0:57

Andre Knob · Accepted Answer · 2018-10-16 00:48:50Z

3

This happens because on this code

new Date(currentTime + daysToAdd*secondsInDay);

secondsInDay is a representation in seconds, and currentTime is represented in ms. If you multiply your secondsInDay by 1000 (to get the equivalent value in ms) you will get the desired date.

answered Oct 16, 2018 at 0:48

Andre Knob

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Comments

Narendra · Accepted Answer · 2018-10-16 00:49:22Z

3

Instead of

var d = new Date(currentTime + daysToAdd*secondsInDay);

you can use

d.setDate(new Date().getDate()+3);

answered Oct 16, 2018 at 0:49

Narendra

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FlokiTheFisherman · Accepted Answer · 2018-10-16 00:49:49Z

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Youre problem is that the constructor of the date object uses MILISECONDS to calculate the date, and you're using SECONDS to add that 3 extra days. Instead of 86400 (seconds) you need to use the value 86400000 (miliseconds).

Goodbye!

answered Oct 16, 2018 at 0:49

FlokiTheFisherman

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Erlisar Vasquez · Accepted Answer · 2018-10-16 00:57:05Z

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You can add the number of days directly to d.getDate()

var d = new Date(2019, 9, 14);
  var daysToAdd = 3;
  var new_day = d.getDate() + daysToAdd;
  var new_d = new Date(d.getFullYear(), d. getMonth(), new_day);

  alert('result in Y-M-D is: ' + new_d.getFullYear() + '-' + new_d. getMonth() + '-' + new_day);

edited Oct 16, 2018 at 0:57

answered Oct 16, 2018 at 0:51

Erlisar Vasquez

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