1. Age Calculation
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. Unit is supplied as text (upper or lower case), using any one of these values:
Note: 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.
Next anniversary date
To calculate the next anniversary date, you can use a formula based on the EDATE and DATEDIF functions. In the example shown, the formula in D5 is: =EDATE(B5,(DATEDIF(B5,C5,"y")+1)*12) This formula will...
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.
Excel YEARFRAC Function
The Excel YEARFRAC function returns a decimal value that represents fractional years between two dates. You can use YEARFRAC for formulas that do things like like calculating age in years using 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