DATEDIF for date differences in Excel - Step-by-Step Guide

Introduction

DATEDIF helps you find the difference between two dates in days, months, or years. It is useful when you want to know how much time has passed between two events, like calculating age or project duration.

When you want to calculate a person's age from their birthdate and today's date.

When you need to find how many months have passed between a project start and end date.

When you want to know the exact number of days between two appointments.

When you want to calculate the number of complete years between two dates for service duration.

When you want to track how many months remain until a deadline.

Steps

Step 1: Click

- a blank cell where you want the result

The cell is selected and ready for typing

Step 2: Type

- the formula bar

The formula appears in the cell as you type

💡 Start typing =DATEDIF( to see the function suggestions

Step 3: Enter

- the formula: =DATEDIF(start_date, end_date, unit)

The cell shows the difference between the two dates based on the unit you choose

💡 Replace start_date and end_date with cell references or dates in quotes, and unit with "d", "m", or "y"

Step 4: Press Enter

- after typing the formula

Excel calculates and displays the date difference

Before vs After

Before

Cell A1 has 2023-01-01, Cell B1 has 2024-06-01, Cell C1 is empty

After

Cell C1 shows 517 when formula =DATEDIF(A1, B1, "d") is entered

Settings Reference

start_date

📍 inside the DATEDIF formula

The earlier date to start counting from

Default: none

end_date

📍 inside the DATEDIF formula

The later date to count up to

Default: none

unit

📍 inside the DATEDIF formula

Defines how the difference is measured

Default: none

Common Mistakes

Using end_date before start_date

DATEDIF returns an error if the start date is after the end date

Always put the earlier date first as start_date and the later date second as end_date

Typing unit without quotes

The unit must be a text string in quotes, otherwise Excel shows an error

Always put the unit inside double quotes, like "d", "m", or "y"

Using DATEDIF with invalid dates or text

If dates are not valid Excel dates, the formula will not calculate correctly

Make sure start_date and end_date are valid dates or cell references containing dates

Summary

DATEDIF calculates the difference between two dates in days, months, or years.

You must enter the earlier date first and the later date second.

The unit argument must be a text string in quotes: "d", "m", or "y".