Software & Apps MS Office Excel DAYS360 Function: Count Days Between Dates Subtract dates in Excel with the DAYS360 function By Ted French Writer Former Lifewire writer Ted French is a Microsoft Certified Professional who teaches and writes about spreadsheets and spreadsheet programs. our editorial process Ted French Updated July 05, 2019 Ted French MS Office Excel Word Powerpoint Outlook Tweet Share Email The DAYS360 function can be used to calculate the number of days between two dates based on a 360-day year (twelve 30-day months). A 360-day calendar is often used in accounting systems, financial markets, and in computer models. An example use for the function would be to compute payment schedules for accounting systems that are based on twelve 30-day months. Syntax and Arguments A function's syntax refers to the layout of the function and includes the function's name, brackets, comma separators, and arguments. The syntax for the DAYS360 function is: = DAYS360 ( Start_date , End_date , Method ) Start_date - (required) the start date of the chosen time period This argument can be a date entered into the function, or a named range or a cell reference to the location of the data in the worksheet.If actual dates are entered as the function's arguments, they must be surrounded by double quotation marks, as shown in line 5 in the image above. End_date - (required) the end date of the chosen time period This argument can be a date entered into the function or a named range or cell reference to the location of the data in the worksheet.If End_date is earlier than the Start_date argument, a negative number is returned, as shown in row 11 of the image, where Dec 31, 2016, is the Start_date and Jan 30, 2016, is the End_date. Method - (optional) a logical or Boolean value (TRUE or FALSE) that specifies whether to use the U.S. (NASD) or European method in the calculation. If TRUE - the function uses the European method of calculating start and end dates.If FALSE - the function uses the U.S. method of calculating start and end dates.If omitted - the function uses the U.S. method. #VALUE! Error Value The DAYS360 function returns the #VALUE! error value if: Start_date or End_date are not valid dates.Start_date or End_date is prior to January 1, 1900 (January 1, 1904, on Macintosh systems). Note: Excel carries out date calculations by converting the dates to serial numbers, which begin at zero for the fictitious date January 0, 1900, on Windows computers and January 1, 1904, on Macintosh computers. Example In the image above, we use the DAYS360 function to add and subtract a various number of months to the date January 1, 2016. The information below covers the steps used to enter the function into cell B6 of the worksheet. Entering the DAYS360 Function Options for entering the function and its arguments include: Typing the complete function: =DAYS360(A1,B2) into cell B3.Selecting the function and its arguments using the DAYS360 function dialog box. Although it is possible to just enter the complete function manually, many people find it easier to use the dialog box, as it takes care of entering the function's syntax, such as brackets, comma separators between arguments, and the quotation marks around dates entered directly as the function's arguments. The steps below cover entering the DAYS360 function shown in cell B3 in the image above using the function's dialog box. Subtracting Months Click on cell B3 to make it the active cell.Click on the Formulas tab of the ribbon.Click on Date and Time functions to open the function drop-down list.Click on DAYS360 in the list to bring up the function's dialog box.Click on the Start_date line in the dialog box.Click on cell A1 in the worksheet to enter that cell reference into the dialog box as the Start_date argument.Click on the End_date line.Click on cell B2 in the worksheet to enter that cell reference into the dialog box.Click OK to close the dialog box and return to the worksheet.The value 360 should be present in cell B3, since according to the 360-day calendar, there are 360 days between the first and last days of the year.If you click on cell B3, the complete function =DAYS360(A1,B2) appears in the formula bar above the worksheet. Method Argument Differences The different combinations of days per month and days per year for the Method argument of the DAYS360 function are available because businesses in various fields — such as share trading, economics, and finance — have different requirements for their accounting systems. By standardizing the number of days per month, businesses can make month to month, or year to year, comparisons that would not normally be possible given that the number of days per month might range from 28 to 31 in a year. These comparisons might be for profits, expenses, or in the case of the financial field, the amount of interest earned on investments. U.S. (NASD - National Association of Securities Dealers) method: If the Start_date is the last day of a month, it becomes equal to the 30th day of the same month.If the End_date is the last day of a month and the Start_date is earlier than the 30th day of a month, the End_date becomes equal to the 1st day of the next month; otherwise, the End_date becomes equal to the 30th day of the same month. European method: Start_dates and End_dates that occur on the 31st day of the month become equal to the 30th day of the same month.When End_date falls on the last day of February, the actual date is used.