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var addmonths = require("addmonths")

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addmonths v1.0.1

Adds or sustract X months to any JavaScript Date.


npm Version License

Adds or sustract X months to any JavaScript Date.

🚧 This Package Is Depreacted 🚧

This package is deprecated in favor of @jsbits/add-months.

Unlike addMonths, @jsbits/add-months handles changes in the timezone correctly, has better support, 100% coverage, and the version for Date.prototype is more consistent with other Date methods.

This package will no longer be updated



npm i addmonths --save


bower install addmonths --save


<script src=""></script>
<!-- ...or to inject `addMonths` to `Date.prototype` -->
<script src=""></script>


newdate = addMonths(startdate, count)

The addMonths function returns a date occurring count months after startdate or, if count is negative, the date occurring count months before startdate.

If there is an overflow in the day, the date is adjusted to the last valid day of the expected month.

If startdate is not a date, returns startdate without changes.

If startdate is an invalid date (i.e. NaN), returns a new Date instance with an invalid date.

If count is evaluated as zero, returns a new Date instance with the same value as startdate.


const addMonths = require('addmonths')

addMonths(new Date(2017, 0, 1), 2)    // 2017-01-01 ==> 2017-03-01
addMonths(new Date(2017, 0, 1), -1)   // 2017-01-01 ==> 2016-12-01
addMonths(new Date(2016, 0, 31), 1)   // 2016-01-31 ==> 2016-02-29
addMonths(new Date(2016, 0, 31), 0)   // new instance with the same value
addMonths('2017-06-12', 1)            // the same string

If you prefer, you can inject the function into the Date prototype of Date requiring "auto" or by loading the IIFE from "dist/" in your browser:


const date = new Date().addMonths(3)

What's New

  • Production ready version.
  • Updated tests.
  • Updated devDependencies.


The MIT License (MIT)

Copyright (c) 2017 Alberto Martínez (

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