YEARFRAC

YEARFRAC(start_date, end_date [,basis])

Returns the number of years as a decimal between two dates.

start_date	The starting date.
end_date	The finishing date.
basis	(Optional) The type of day counting to use: 0 = 30/360 (default) 1 = Actual/Actual 2 = Actual/360 3 = Actual/365 4 = 30E/360

REMARKS

* All arguments are truncated to integers.
* Dates may be entered as text strings within quotation marks, as serial numbers or as results of other formulas or functions.
* If "start_date" or "end_date" are not valid dates, then #NUM! is returned.
* If "start_date" can be a text string or a date serial number.
* If "basis" is left blank, then 0 is used.
* If "basis" is not an integer, it is truncated.
* If "basis" < 0, then #NUM! is returned.
* If "basis" > 4, then #NUM! is returned.
* If "basis" = 0, the calculation is based on 30 days in every month, divided by 360.
* If "basis" = 1 (Actual/Actual), the calculation is based on the actual number of days in the month, divided by the actual number of days in the year.
* If "basis" = 2 (Actual/360), the calculation is based on the actual number of days in the month, divided by 360.
* If "basis" = 3 (Actual/365), the calculation is based on the actual number of days in the month, divided by 365.
* If "basis" = 4 (European 30/360), the calculation is based on 30 days in a month, divided by 360.
* You can use the DAYS360 function to return the number of days between two dates, based on 30 day months.
* You can use the YEAR function to return the year as an integer given a date serial number.
* For the Microsoft documentation refer to support.microsoft.com
* For the Google documentation refer to support.google.com

	A
1	=YEARFRAC("2001/01/25", "2001/09/27") = 0.672
2	=YEARFRAC("01/01/2018", "31/12/2018") = 1
3	=YEARFRAC("01/01/2018", "31/07/2018") = 0.583333333333333
4	=YEARFRAC("01 Jan 2020", "01 April 2020", 0) = 0.25
5	=YEARFRAC("01 Jan 2020", "01 April 2020", 1) = 0.248633879781421
6	=YEARFRAC("01 Jan 2020", "01 April 2020", 2) = 0.252777777777778
7	=YEARFRAC("01 Jan 2020", "01 April 2020", 3) = 0.249315068493151
8	=YEARFRAC("01 Jan 2020", "01 April 2020", 4) = 0.25
9	=YEARFRAC("01/01/2018", "31/04/2018") = #VALUE!
10	=YEARFRAC("1/1/1998", "6/30/1998", 2) = #VALUE!
11	=YEARFRAC("1/1/1998", "6/30/1998", 0) = #VALUE!