EXCEL: know about YEARFRAC()

It calculates the fraction of the year represented by the number of whole days between two dates (the start_date and the end_date). Use the YEARFRAC worksheet function to identify the proportion of a whole year's benefits or obligations to assign to a specific term.

Syntax

YearFrac(Arg1, Arg2, Arg3)

Parameters

Name	Required/Optional	Data Type	Description
Arg1	Required	Variant	Start_date - a date that represents the start date.
Arg2	Required	Variant	End_date - a date that represents the end date.
Arg3	Optional	Variant	Basis - the type of day count basis to use.

 Important   Dates should be considered by using the DATE function, or as results of other formulas or functions. For example, use DATE(2008,5,23) for the 23rd day of May, 2008. Problems can occur if dates are entered as text.

Basis	Day count basis
0 or omitted	US (NASD) 30/360
1	Actual/actual
2	Actual/360
3	Actual/365
4	European 30/360

• Microsoft Excel stores dates as sequential serial numbers so they can be used in calculations. By default, January 1, 1900 is serial number 1, and January 1, 2008 is serial number 39448 because it is 39,448 days after January 1, 1900. Microsoft Excel for the Macintosh uses a different date system as its default.
• All arguments are truncated to integers.
• If start_date or end_date are not valid dates, YEARFRAC returns the #VALUE! error value.
• If basis < 0 or if basis > 4, YEARFRAC returns the #NUM! error value.