The setMonth() method of Date instances changes the month and/or day of the month for this date according to local time.

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setMonth(monthValue, dateValue)



An integer representing the month: 0 for January, 1 for February, and so on.

dateValue Optional

An integer from 1 to 31 representing the day of the month.

Return value

Changes the Date object in place, and returns its new timestamp. If a parameter is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.


If you do not specify the dateValue parameter, the same value as what is returned by getDate() is used.

If a parameter you specify is outside of the expected range, other parameters and the date information in the Date object are updated accordingly. For example, if you specify 15 for monthValue, the year is incremented by 1, and 3 is used for month.

The current day of month will have an impact on the behavior of this method. Conceptually it will add the number of days given by the current day of the month to the 1st day of the new month specified as the parameter, to return the new date. For example, if the current value is 31st January 2016, calling setMonth with a value of 1 will return 2nd March 2016. This is because in 2016 February had 29 days.


Using setMonth()

const theBigDay = new Date();

//Watch out for end of month transitions
const endOfMonth = new Date(2016, 7, 31);
console.log(endOfMonth); //Wed Mar 02 2016 00:00:00


ECMAScript Language Specification
# sec-date.prototype.setmonth

Browser compatibility

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See also