Months Between Dates Excel Formula

Calculating Months Between Dates in Excel

To calculate the months between two dates in Excel, you can use several formulas, depending on whether you want to include the months that are not complete or just the full months. The most straightforward way to achieve this is by using the DATEDIF function, which is specifically designed for calculating the difference between two dates in various units, such as days, months, and years.

Using the DATEDIF Function

The DATEDIF function has the following syntax:

DATEDIF(start_date, end_date, unit)

• start_date is the starting date.
• end_date is the ending date.
• unit specifies the unit of time, which can be “D” for days, “M” for months, “Y” for years, etc.

To calculate the months between two dates, you would use “M” as the unit:

=DATEDIF(A1, B1, "M")

Assuming A1 contains the start date and B1 contains the end date.

Understanding the DATEDIF Function’s Behavior

It’s crucial to understand how DATEDIF behaves, especially with the “M” unit. This function calculates the difference in months by subtracting the months and then adjusting for the day. If the day of the end date is before the day of the start date, it subtracts one from the result. This means if you’re calculating the months between January 31st and February 1st, DATEDIF will return 1 month, even though only one day has passed.

Alternative Method Using the EOMONTH Function

For a more precise calculation that counts full months, you can use the EOMONTH function in combination with DATEDIF:

=DATEDIF(EOMONTH(A1, -1), EOMONTH(B1, 0), "M") + 1

However, this formula counts the month of the start date and might not be what you’re looking for if you want to exclude the starting month or only count full months between the dates.

Calculating Full Months Between Dates

If you’re looking to count only full months (i.e., if the start date is the 15th of January and the end date is the 14th of February, it should not count February), you can use the following formula:

=DATEDIF(DATE(YEAR(A1), MONTH(A1) + 1, 0), DATE(YEAR(B1), MONTH(B1), 1), "M")

This formula calculates the difference by adjusting the start and end dates to the first day of the next month after the start date and the first day of the month of the end date, effectively excluding any incomplete months at the beginning and end.

Example Usage

Suppose you have two dates in cells A1 and B1: - A1: January 15, 2022 - B1: February 14, 2022

Using the DATEDIF function with “M” as the unit:

=DATEDIF(A1, B1, "M")

This will return 1, indicating one month difference, even though February is not complete.

Table for Comparison

Start Date	End Date	DATEDIF(A1, B1, “M”)	Description
January 1, 2022	January 31, 2022	0	No month difference, same month.
January 31, 2022	February 1, 2022	1	One month difference, even though only one day apart.
January 15, 2022	February 14, 2022	1	Counts February, even though it’s not complete.

📝 Note: The DATEDIF function does not handle dates before January 1, 1900, correctly, so ensure your dates are within this range.

To summarize, calculating months between dates in Excel can be achieved with the DATEDIF function, which offers a straightforward way to get the difference in months. However, understanding its behavior, especially concerning incomplete months, is crucial for accurate calculations. Alternative methods, such as adjusting the start and end dates, can provide more precise control over what constitutes a “month” in your specific scenario. By choosing the right formula, you can efficiently manage date calculations in your Excel spreadsheets.