To increment months in dates in Excel, you can use the EDATE function. This function takes a date and an integer as arguments, and returns a new date that is the specified number of months before or after the original date.

For example, if the cell A1 contains the date 1/1/2019, then the formula =EDATE(A1,1) will return the date 2/1/2019. And if the cell A1 contains the date 12/31/2018, then the formula =EDATE(A1,-1) will return the date 11/30/2018. You can use this technique to increment or decrement dates by any number of months.

Note: The EDATE function will return an error if the resulting date is not a valid Excel date. For example, if you try to increment a date by more than 12 months using EDATE, you will get an error. To avoid this, you can use the DATE function in conjunction with EDATE, as shown in the examples below.

Examples

Incrementing a Date by 1 Month

// Incrementing a date by 1 month
 A1: 1/1/2019
 B1: =EDATE(A1,1)  // returns 2/1/2019

 A1: 2/28/2019
 B1: =EDATE(A1,1)  // returns 3/31/2019

 A1: 2/29/2020
 B1: =EDATE(A1,1)  // returns 3/31/2020 (leap year)

Incrementing a Date by Multiple Months

// Incrementing a date by multiple months
 A1: 1/31/2019    // start date
 B2: 3            // number of months to increment

 B3: =DATE(YEAR(A2),MONTH(A2)+B2,DAY(A2))  // returns 4/30/2019

 A4: 2/28/2020    // start date (leap year)  
 B5: 13           // number of months to increment

 B6: =DATE(YEAR(A4),MONTH(A4)+B5,DAY(A4))  // returns 3/31/2021 (non-leap year)