JavaScript function to add X months to a date

Question

I’m looking for the easiest, cleanest way to add X months to a JavaScript date.

I’d rather not handle the rolling over of the year or have to write my own function.

Is there something built in that can do this?

Answer 1

I think this should do it:

var x = 12; //or whatever offset
var CurrentDate = new Date();
CurrentDate.setMonth(CurrentDate.getMonth() + x);

I believe it should automatically handle incrementing to the appropriate year and mod-ing to the appropriate month.

try it

Answer 2

var a=new Date();
a.setDate(a.getDate()+5);

As above stated method, you can add month to Date function.

Answer 3

As most of the answers highlighted, we could use setMonth() method together with getMonth() method to add specific number of months to a given date.

Example: (as mentioned by @ChadD in his answer. )

var x = 12; //or whatever offset 
var CurrentDate = new Date();
CurrentDate.setMonth(CurrentDate.getMonth() + x);

But we should carefully use this solution as we will get trouble with edge cases.

To handle edge cases, answer which is given in following link is helpful.

https://stackoverflow.com/a/13633692/3668866

Answer 4

Sometimes useful create date by one operator like in BIRT parameters

I made 1 month back with:

new Date(new Date().setMonth(new Date().getMonth()-1));   

Answer 5

Taken from @bmpsini and @Jazaret responses, but not extending prototypes: using plain functions (Why is extending native objects a bad practice?):

function isLeapYear(year) { 
    return (((year % 4 === 0) && (year % 100 !== 0)) || (year % 400 === 0)); 
}

function getDaysInMonth(year, month) {
    return [31, (isLeapYear(year) ? 29 : 28), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31][month];
}

function addMonths(date, value) {
    var d = new Date(date),
        n = date.getDate();
    d.setDate(1);
    d.setMonth(d.getMonth() + value);
    d.setDate(Math.min(n, getDaysInMonth(d.getFullYear(), d.getMonth())));
    return d;
}

Use it:

var nextMonth = addMonths(new Date(), 1);

Answer 6

The following is an example of how to calculate a future date based on date input (membershipssignup_date) + added months (membershipsmonths) via form fields.

The membershipsmonths field has a default value of 0

Trigger link (can be an onchange event attached to membership term field):

<a href="#" onclick="calculateMshipExp()"; return false;">Calculate Expiry Date</a>

function calculateMshipExp() {

var calcval = null;

var start_date = document.getElementById("membershipssignup_date").value;
var term = document.getElementById("membershipsmonths").value;  // Is text value

var set_start = start_date.split('/');  

var day = set_start[0];  
var month = (set_start[1] - 1);  // January is 0 so August (8th month) is 7
var year = set_start[2];
var datetime = new Date(year, month, day);
var newmonth = (month + parseInt(term));  // Must convert term to integer
var newdate = datetime.setMonth(newmonth);

newdate = new Date(newdate);
//alert(newdate);

day = newdate.getDate();
month = newdate.getMonth() + 1;
year = newdate.getFullYear();

// This is British date format. See below for US.
calcval = (((day <= 9) ? "0" + day : day) + "/" + ((month <= 9) ? "0" + month : month) + "/" + year);

// mm/dd/yyyy
calcval = (((month <= 9) ? "0" + month : month) + "/" + ((day <= 9) ? "0" + day : day) + "/" + year);

// Displays the new date in a <span id="memexp">[Date]</span> // Note: Must contain a value to replace eg. [Date]
document.getElementById("memexp").firstChild.data = calcval;

// Stores the new date in a <input type="hidden" id="membershipsexpiry_date" value="" name="membershipsexpiry_date"> for submission to database table
document.getElementById("membershipsexpiry_date").value = calcval;
}