The DAYS360 function with examples in Excel

 The DAYS360 function in Excel calculates the number of days between two dates based on a 360-day year (twelve 30-day months). This function is commonly used in financial calculations where a simplified day count convention is applied. Here’s how it works:

1. Basic Syntax:

   • The DAYS360 function has the following format:

     =DAYS360(start_date, end_date, [method])
     

   • Where:
     • start_date: The beginning date.
     • end_date: The ending date.
     • [method] (optional): A logical value that specifies whether to use the U.S. or European method in the calculation.

2. Method Options:

   • When method is FALSE (default), the U.S. method is used:
     • If the start date is the last day of a month, it becomes equal to the 30th day of that month.
     • If the end date is the last day of a month and the start date is earlier than the 30th day of that month, the end date becomes the 1st day of the next month; otherwise, the end date is the 30th day of the same month.
   • When method is TRUE, the European method is used:
     • Starting and ending dates that occur on the 31st day of a month become equal to the 30th day of the same month.

3. Examples:

   • To calculate the number of days between January 1, 2023, and December 31, 2023, using the default 30/360 day count convention:

     =DAYS360("01-Jan-2023", "31-Dec-2023")
     

     This returns 360 days.

   • For more flexibility, you can use cell references. Suppose you have the start date (July 1, 2023) in cell A1 and the end date (December 31, 2023) in cell B1. The formula below returns 180 days:

     =DAYS360(A1, B1)
     

Remember that Excel stores dates as sequential serial numbers, with January 1, 1900, as serial number 1.