The DAYS360 Function in Excel is categorized under Excel Date/Time functions. This function helps to calculate the number of days between two dates, based on a 360day year.
As a finacial analyst, the DAYS360 Function in Excel becomes useful in preparing reports such as an Aging schedule for debtors or computing a payments schedule for accounting systems that are based on twelve 30day months.
Syntax: DAYS360(start_date,end_date,[method])
The DAYS360 function syntax has the following arguments:
 Start_date – This is a required argument. It is the start of the period.
 End_date – This is a required argument. It is the end of the period.
 Method – This is an optional argument. It is a Boolean value. Here we specify the method to be used in the calculation. The method can either be:


 False or omitted – US (NASD) method used. Under this method:
 When the starting date is the last day of a month, it is set as the 30th day of the same month.
 Whereas, when the ending date is the last day of a month then:
 If the start date is the last day of the month, the end date is set to the 1st of the following month.
 Otherwise, the end date is set to the 30th of that month.
 True – European method used. Here, the starting dates and ending dates that occur on the 31st day of a month become equal to the 30th day of the same month.
 False or omitted – US (NASD) method used. Under this method:

Example: Let’s look at some Excel DAYS360 function examples and explore how to use the DAYS360 function as a worksheet function in Microsoft Excel:
Syntax: =DAYS360(A2,B2)
Result:
Based on the Excel spreadsheet above, the following DAYS360 examples would return:
Syntax: =DAYS360(A3,B3,TRUE)
Result: 29
Syntax: =DAYS360(A3,B3,FALSE)
Result: 30
Syntax: =DAYS360(A5,DATE(2015,2,2))
Result: 1
Syntax: =DAYS360(A6,B6,TRUE)
Result: 29
Syntax: =DAYS360(A7,B7,TRUE)
Result: 31
Syntax: =DAYS360(A8,B8,FALSE)
Result: 94
Syntax: =DAYS360(A9,B9)
Result: 30
Syntax: =DAYS360(A10,B10)
Result: 360
Syntax: =DAYS360(A11,B11)
Result: 1
Syntax: =DAYS360(A12,B12)
Result: 360
Note:
 #NUM! error – This occurs when the start_date and the end_date arguments are numerical values but are not recognized as valid dates.
 #VALUE! error – This occurs when the:
 One or both of the given arguments – start_date or end_date – are text values that cannot be interpreted as dates.
 The arguments given are nonnumeric.