How to use the Excel DATEDIF function

Summary

The Excel DATEDIF function returns the difference between two date values in years, months, or days. The DATEDIF (Date + Dif) function is a "compatibility" function that comes from Lotus 1-2-3. For reasons unknown, it is only documented in Excel 2000, but you can use it in your formulas in all Excel versions since that time.

Note: Excel won't help you fill out the arguments for DATEDIF like other functions, but it will work when configured correctly.

Purpose

Get days, months, or years between two dates

Return value

A number representing time between two dates

Syntax

=DATEDIF (start_date, end_date, unit)

Arguments

start_date - Start date in Excel date serial number format.
end_date - End date in Excel date serial number format.
unit - The time unit to use (years, months, or days).

Usage notes

The DATEDIF (Date + Dif) function is a "compatibility" function that comes from Lotus 1-2-3. For reasons unknown, it is only documented in Excel 2000, but it works in all Excel versions since that time. As Chip Pearson says: DATEDIF is treated as the drunk cousin of the Formula family. Excel knows it lives a happy and useful life, but will not speak of it in polite conversation.

The DATEDIF function calculates the time between a start_date and an end_date in years, months, or days. The time unit to return is specified using the unit argument, which is supplied as text (upper or lower case).

Examples

In the example shown, column B contains the date January 1, 2016 and column C contains the date March 1, 2018. In column E:

E5=DATEDIF(B5,C5,"y") // returns 2
E6=DATEDIF(B6,C6,"m") // returns 26
E7=DATEDIF(B7,C7,"d")// returns 790

The table below summarizes available unit values and the result for each:

Unit	Result
"Y"	Difference in complete years
"M"	Difference in complete months
"D"	Difference in days
"MD"	Difference in days, ignoring months and years
"YM"	Difference in months, ignoring days and years
"YD"	Difference in days, ignoring years

Notes

Excel will not help you fill in the DATEDIF function like other functions.
DATEDIF with throw a #NUM error if start date is greater than the end date. If you are working with a more complex formula where start dates and end dates may be unknown, or out of bounds, you can trap the error with the IFERROR function, or use MIN and MAX to sort out dates.
Microsoft recommends not using the "MD" value for unit because it "may result in a negative number, a zero, or an inaccurate result". If you need to calculate days between dates ignoring year and month values, you can use the formula explained here.

Related functions

Excel NETWORKDAYS Function

The Excel NETWORKDAYS function calculates the number of working days between two dates. NETWORKDAYS automatically excludes weekends (Saturday and Sunday) and can optionally exclude a list of holidays supplied as dates.

NETWORKDAYS ...

Excel YEARFRAC Function

The Excel YEARFRAC function returns a decimal value that represents fractional years between two dates. You can use YEARFRAC to do things like calculate age with a birthdate.

Excel DAYS360 Function

The Excel DAYS360 function returns the number of days between two dates based on a 360-day year. Calculations based on a 360-day year comes from certain accounting calculations where all 12 months are considered to have 30 days.

Good links

Microsoft DATEDIF function documentation

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