What is the DATEDIF Function
The DATEDIF function calculates the difference between two dates in years, months, or days. It is very useful for calculating age, tenure, and duration. Note that DATEDIF is an undocumented function, so Excel will not autocomplete it, but it works reliably.
Formula: =DATEDIF(start_date, end_date, unit)
Practical Example 1
Birth date in A2, today in B2.
Type: =DATEDIF(A2, B2, Y)
Result: age in full years
Practical Example 2
Calculate months of service for an employee.
Type: =DATEDIF(A2, B2, M)
Result: total months between the two dates
Practical Example 3
Calculate days between two dates.
Type: =DATEDIF(A2, B2, D)
Result: total days between the two dates
Practical Example 4
Calculate completed years and months together using two DATEDIF calls.
Type: =DATEDIF(A2, B2, Y) & years & DATEDIF(A2, B2, YM) & months
Result: a combined age string like 5 years 3 months
When to Use It
DATEDIF is used for age calculation in HR and education, tenure calculation for employees, project duration tracking, service year counting, and any scenario where you need the gap between two dates.