DAYS360:
Calculates the number of days between two dates based on a 360day year
The DAYS360 function calculates 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.
Using the DAYS360 function:
The arguments for the DAYS360 function are:
Argument

Required?

Description

start_date 
Required 
The starting date of the period you are calculating the number of days between. 
end_date 
Required 
The ending date of the period you are calculating the number of days between. 
method 
Optional 
A logical value that specifies whether to use the U.S. or European method in the calculation:
• FALSE or omitted 
U.S. (NASD) method. If the starting date is the last day of a month, it becomes equal to the 30th day of the same month.
If the ending date is the last day of a month and the starting date is earlier than the 30th day of a month,
the ending date becomes equal to the 1st day of the next month; otherwise the ending date becomes equal to the 30th day of the same month. 
• TRUE 
European method. Starting dates and ending dates that occur on the 31st day of a month become equal to the 30th day of the same month. 

The DAYS360 function calculates 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.