This article describes the formula syntax and usage of the YEARFRAC function (function: A prewritten formula that takes a value or values, performs an operation, and returns a value or values. Use functions to simplify and shorten formulas on a worksheet, especially those that perform lengthy or complex calculations.) in Microsoft Excel.
Description
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(start_date, end_date, [basis])
The YEARFRAC function syntax has the following arguments (argument: A value that provides information to an action, an event, a method, a property, a function, or a procedure.):
 Start_date Required. A date that represents the start date.
 End_date Required. A date that represents the end date.
 Basis Optional. The type of day count basis to use.
Basis 
Day count basis 
0 or omitted 
US (NASD) 30/360 
1 
Actual/actual 
2 
Actual/360 
3 
Actual/365 
4 
European 30/360 
Important Dates should be entered 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.
Remarks
 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.
 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.
Example
The example may be easier to understand if you copy it to a blank worksheet.
How do I copy an example?
 Select the example in this article. If you are copying the example in Excel Online, copy and paste one cell at a time.
Important: Do not select the row or column headers.
Selecting an example from Help
 Press CTRL+C.
 Create a blank workbook or worksheet.
 In the worksheet, select cell A1, and press CTRL+V. If you are working in Excel Online, repeat copying and pasting for each cell in the example.
Important: For the example to work properly, you must paste it into cell A1 of the worksheet.
 To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.
After you copy the example to a blank worksheet, you can adapt it to suit your needs.

A 
B 
Data 
Description 
1/1/2007 
Start date 
7/30/2007 
End date 
2 
Actual/360 (see above) 
Formula 
Description (Result) 
=YEARFRAC(A2,A3,A4) 
Fraction of the year between the two dates (0.583333333) 

Note In Excel Online, to view the result in its proper format, select the cell, and then on the Home tab, in the Number group, click the arrow next to Number Format, and click General.