DAYS360

DAYS360(start_date, end_date [,method])

Returns the number of days between two dates, based on 30 day months.

start_date	The first date or starting date of the period.
end_date	The last date or ending date of the period.
method	(Optional) A logical value indicating which method to use: True = European method False = US method (default)

REMARKS

* The calendar used is based on a 360 day year with twelve 30 day months.
* The "date" arguments can be entered as text strings within quotation marks, as serial numbers or as results of other formulas or functions.
* If "start_date" is the 31st of a month then the 30th of that month is used.
* If "start_date" > "end_date", then a negative number is returned.
* If "start_date" is not a valid date, then #VALUE! is returned.
* If "end_date" is not a valid date, then #VALUE! is returned.
* If "method" = False, then any ending dates that occur on the 31st of a month become equal to the 1st of the next month (US, NASD).
* If "method" = True, then any ending dates that occur on the 31st of a month become the 30th of that month (European).
* If "method" is left blank, then False (US, NASD) is used.
* This function is useful for some accountancy systems that use a 360 day calendar.
* The date format can be any of those found on the "Format Cells" dialog box.
* You can use the DAY function to return the day as an integer given a date serial number.
* You can use the DAYS function to return the number of days between two dates.
* You can use the NETWORKDAYS.INTL function to return the number of days excluding weekends and holidays.
* You can use the WORKDAY.INTL function to return a given number of working days before or after a date.
* You can use the YEARFRAC function to return the number of years as a decimal between two dates.
* For the Microsoft documentation refer to support.microsoft.com

	A	B
1	=DAYS360("1 Jan 2007","1 Jan 2007") = 0	1/1/2007
2	=DAYS360("1 Jan 2007","2 Jan 2007") = 1	1/2/2007
3	=DAYS360("1/1/2007","9/1/2007") = 8	1/3/2007
4	=DAYS360(B1,B9) = 8	1/4/2007
5	=DAYS360("1 Jan 2007","30 Jan 2007") = 29	1/5/2007
6	=DAYS360("1 Jan 2007","31 Jan 2007") = 30	1/6/2007
7	=DAYS360("1 Jan 2007","1 Feb 2007") = 30	1/7/2007
8	=DAYS360("30 Jan 2007","02 Feb 2007") = 2	1/8/2007
9	=DAYS360("31 Jan 2007","02 Feb 2007") = 2	1/9/2007
10	=DAYS360("31 Jan 2007","02 Feb 2007",TRUE) = 2
11	=DAYS360("31 Jan 2007","02 Feb 2007",FALSE) = 2
12	=DAYS360("1 Jan 2007","31 Dec 2007") = 360
13	=DAYS360("14 Jan 2007","1 Jan 2007") = -13
14	=DAYS360(1/1/2007,31/12/2007) = 0
15	=DAYS360(DATE(2007,1,1),DATE(2007,12,31)) = 360
16	=DAYS360("1/30/1998","2/1/1998") = #VALUE!
17	=DAYS360("01/03/2004","31/06/2004",TRUE) = #VALUE!
18	=DAYS360("03/16/2009","03/16/2008") = #VALUE!

3 & 12 - You should always put your dates as a text string rather than just in a date format.
10 - You should always try and use the DATE function to ensure you get the correct value.