How to add days to Date?

If you can, use moment.js. JavaScript doesn't have very good native date/time methods. The following is an example Moment's syntax:

var nextWeek = moment().add(7, 'days'); alert(nextWeek);

Reference: http://momentjs.com/docs/#/manipulating/add/

I created these extensions last night: you can pass either positive or negative values;

example:

var someDate = new Date();
var expirationDate = someDate.addDays(10);
var previous = someDate.addDays(-5);


Date.prototype.addDays = function (num) {
    var value = this.valueOf();
    value += 86400000 * num;
    return new Date(value);
}

Date.prototype.addSeconds = function (num) {
    var value = this.valueOf();
    value += 1000 * num;
    return new Date(value);
}

Date.prototype.addMinutes = function (num) {
    var value = this.valueOf();
    value += 60000 * num;
    return new Date(value);
}

Date.prototype.addHours = function (num) {
    var value = this.valueOf();
    value += 3600000 * num;
    return new Date(value);
}

Date.prototype.addMonths = function (num) {
    var value = new Date(this.valueOf());

    var mo = this.getMonth();
    var yr = this.getYear();

    mo = (mo + num) % 12;
    if (0 > mo) {
        yr += (this.getMonth() + num - mo - 12) / 12;
        mo += 12;
    }
    else
        yr += ((this.getMonth() + num - mo) / 12);

    value.setMonth(mo);
    value.setYear(yr);
    return value;
}

A solution designed for the pipeline operator:

const addDays = days => date => {
  const result = new Date(date);

  result.setDate(result.getDate() + days);

  return result;
};

Usage:

// Without the pipeline operator...
addDays(7)(new Date());

// And with the pipeline operator...
new Date() |> addDays(7);

If you need more functionality, I suggest looking into the date-fns library.

the simplest answer is, assuming the need is to add 1 day to the current date:

var currentDate = new Date();
var numberOfDayToAdd = 1;
currentDate.setDate(currentDate.getDate() + numberOfDayToAdd );

To explain to you, line by line, what this code does:

Create the current date variable named currentDate. By default "new Date()" automatically assigns the current date to the variable. Create a variable to save the number of day(s) to add to the date (you can skip this variable and use directly the value in the third line) Change the value of Date (because Date is the number of the month's day saved in the object) by giving the same value + the number you want. The switch to the next month will be automatic

Without using the second variable, you can replace 7 with your next x days:

let d=new Date(new Date().getTime() + (7 * 24 * 60 * 60 * 1000));

to substract 30 days use (24h=86400000ms)

new Date(+yourDate - 30 *86400000)

var yourDate=new Date(); var d = new Date(+yourDate - 30 *86400000) console.log(d)

The simplest solution.

Date.prototype.addDays = function(days) { this.setDate(this.getDate() + parseInt(days)); return this; }; // and then call var newDate = new Date().addDays(2); //+2 days console.log(newDate); // or var newDate1 = new Date().addDays(-2); //-2 days console.log(newDate1);

Late to the party, but if you use jQuery then there's an excellent plugin called Moment:

http://momentjs.com/

var myDateOfNowPlusThreeDays = moment().add(3, "days").toDate();

http://momentjs.com/docs/#/manipulating/

And lots of other good stuff in there!

Edit: jQuery reference removed thanks to aikeru's comment

You can use JavaScript, no jQuery required:

var someDate = new Date();
var numberOfDaysToAdd = 6;
someDate.setDate(someDate.getDate() + numberOfDaysToAdd); 
Formatting to dd/mm/yyyy :

var dd = someDate.getDate();
var mm = someDate.getMonth() + 1;
var y = someDate.getFullYear();

var someFormattedDate = dd + '/'+ mm + '/'+ y;

As simple as this:

new Date((new Date()).getTime() + (60*60*24*1000));

Thanks Jason for your answer that works as expected, here is a mix from your code and the handy format of AnthonyWJones :

Date.prototype.addDays = function(days){
    var ms = new Date().getTime() + (86400000 * days);
    var added = new Date(ms);
    return added;
}

Old I know, but sometimes I like this:

function addDays(days) {
    return new Date(Date.now() + 864e5 * days);
}

You can try:

var days = 50;

const d = new Date();

d.setDate(d.getDate() + days)

This should work well.

No, javascript has no a built in function, but you can use a simple line of code

timeObject.setDate(timeObject.getDate() + countOfDays);

I had issues with daylight savings time with the proposed solution.

By using getUTCDate / setUTCDate instead, I solved my issue.

// Curried, so that I can create helper functions like `add1Day`
const addDays = num => date => {
  // Make a working copy so we don't mutate the supplied date.
  const d = new Date(date);

  d.setUTCDate(d.getUTCDate() + num);

  return d;
}

Why so complicated?

Let's assume you store the number of days to add in a variable called days_to_add.

Then this short one should do it:

calc_date = new Date(Date.now() +(days_to_add * 86400000));

With Date.now() you get the actual unix timestamp as milliseconds and then you add as many milliseconds as you want to add days to. One day is 24h60min60s*1000ms = 86400000 ms or 864E5.

Generic prototype with no variables, it applies on an existing Date value:

Date.prototype.addDays = function (days) {
    return new Date(this.valueOf() + days * 864e5);
}

The mozilla docs for setDate() don't indicate that it will handle end of month scenarios. See https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Date

setDate()

Sets the day of the month (1-31) for a specified date according to local time.

That is why I use setTime() when I need to add days.

I guess I'll give an answer as well: Personally, I like to attempt to avoid gratuitous variable declaration, method calls, and constructor calls, as they are all expensive on performance. (within reason, of course) I was going to leave this as just comment under the Answer given by @AnthonyWJones but thought better of it.

// Prototype usage...
Date.prototype.addDays = Date.prototype.addDays || function( days ) {
    return this.setTime( 864E5 * days + this.valueOf() ) && this;
};

// Namespace usage...
namespace.addDaysToDate = function( date, days ) {
    return date.setTime( 864E5 * days + date.valueOf() ) && date;
};

// Basic Function declaration...
function addDaysToDate( date, days ) {
    return date.setTime( 864E5 * days + date.valueOf() ) && date;
};

The above will respect DST. Meaning if you add a number of days that cross DST, the displayed time (hour) will change to reflect that. Example: Nov 2, 2014 02:00 was the end of DST.

var dt = new Date( 2014, 10, 1, 10, 30, 0 );
console.log( dt );                  // Sat Nov 01 2014 10:30:00
console.log( dt.addDays( 10 ) );    // Tue Nov 11 2014 09:30:00

If you're looking to retain the time across DST (so 10:30 will still be 10:30)...

// Prototype usage...
Date.prototype.addDays = Date.prototype.addDays || function( days ) {
    return this.setDate( this.getDate() + days ) && this;
};

// Namespace usage...
namespace.addDaysToDate = function( date, days ) {
    return date.setDate( date.getDate() + days ) && date;
};

// Basic Function declaration...
function addDaysToDate( date, days ) {
    return date.setDate( date.getDate() + days ) && date;
};

So, now you have...

var dt = new Date( 2014, 10, 1, 10, 30, 0 );
console.log( dt );                  // Sat Nov 01 2014 10:30:00
console.log( dt.addDays( 10 ) );    // Tue Nov 11 2014 10:30:00

Short:

function addDays(date, number) {
    const newDate = new Date(date);
    return new Date(newDate.setDate(newDate.getDate() + number));
}

console.log({
    tomorrow: addDays(new Date(), 1)
});

Advance:

function addDays(date, number) {
    const newDate = new Date(date);
    return new Date(newDate.setDate(date.getDate() + number));
}

function addMonths(date, number) {
    const newDate = new Date(date);
    return new Date(newDate.setMonth(newDate.getMonth() + number));
}

function addYears(date, number) {
    const newDate = new Date(date);
    return new Date(newDate.setFullYear(newDate.getFullYear() + number));
}

function getNewDate(dateTime) {
    let date = new Date();
    let number = parseInt(dateTime.match(/\d+/)[0]);

    if (dateTime.indexOf('-') != -1)
        number = (- number);


    if (dateTime.indexOf('day') != -1)
        date = addDays(date, number);

    else if (dateTime.indexOf('month') != -1)
        date = addMonths(date, number);

    else if (dateTime.indexOf('year') != -1)
        date = addYears(date, number);


    return date;
}


console.log({
    tomorrow: getNewDate('+1day'),
    yesterday: getNewDate('-1day'),
    nextMonth: getNewDate('+1month'),
    nextYear: getNewDate('+1year'),
});

With fix provide by jperl