Returns the number of days between two dates based on a 360day year (twelve 30day months), which is used in some accounting calculations. Use this function to help compute payments if your accounting system is based on twelve 30day months.
Syntax
DAYS360(start_date,end_date,method)
Start_date, end_date are the two dates between which you want to know the number of days. If start_date occurs after end_date, DAYS360 returns a negative number. 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.
Method is a logical value that specifies whether to use the U.S. or European method in the calculation.
Method 
Defined 
FALSE or omitted 
U.S. (NASD) method. If the starting date is the last day of a month, it becomes equal to the 30th of the same month. If the ending date is the last day of a month and the starting date is earlier than the 30th of a month, the ending date becomes equal to the 1st of the next month; otherwise the ending date becomes equal to the 30th of the same month. 
TRUE 
European method. Starting dates and ending dates that occur on the 31st of a month become equal to the 30th of the same month. 
Remark
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.
Example
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
 Create a blank workbook or worksheet.
 Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help
 Press CTRL+C.
 In the worksheet, select cell A1, and press CTRL+V.
 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.

A 
Dates 
1/30/2008 
2/1/2008 
Formula 
Description (Result) 
=DAYS360(A2,A3) 
Number of days between the two dates above, based on a 360day year (1) 
