Excel DAYS360 function


The Excel DAYS360 function calculates the number of days between two dates using a 360-day year, where each month is considered to have 30 days. This method is often used in accounting calculations and financial analysis where a standardized year length simplifies interest and payment calculations.
					=DAYS360(start_date, end_date, [method])
  • start_date: The beginning date of the period.
  • end_date: The ending date of the period.
  • method: [Optional] The day count convention to use. FALSE (default) uses the US method; TRUE uses the European method.
Return value
The number of days between the two dates based on a 360-day year.

How to use

Use DAYS360 when you need to calculate the number of days between two dates under the 360-day year assumption. This function is useful in finance and accounting for standardizing calculations across months and years. The optional method argument allows you to choose between US and European day count conventions, affecting how end-of-month dates are treated.


Simple DAYS360
Standard Month Calculation: To calculate the number of days between two dates in a standard month format:
					=DAYS360("2020-03-01", "2020-04-01")
This formula calculates the number of days between March 1, 2020, and April 1, 2020, under the 360-day year convention, resulting in 30 days.
DAYS360 with US Method
US Method Calculation: To calculate days using the US method for end-of-month:
					=DAYS360("2020-08-31", "2020-09-30", FALSE)
This formula calculates the days between August 31, 2020, and September 30, 2020, using the US method, where end-of-month dates are treated as the 30th.
DAYS360 with European Method
European Method Calculation: To calculate days using the European method:
					=DAYS360("2020-08-31", "2020-09-30", TRUE)
Under the European method, both August 31 and September 30 are treated as the 30th, and the formula calculates the number of days accordingly.
DAYS360 for Financial Analysis
Interest Calculation for Loans: To calculate the interest period for a loan using the 360-day convention:
					=DAYS360(loan_start_date, loan_end_date) * daily_interest_rate
This formula calculates the number of days between the start and end dates of a loan, then multiplies it by the daily interest rate for interest calculations.

Additional Notes

  • DAYS360 is particularly useful in financial contexts where a uniform month length simplifies calculations.
  • Be aware of the day count convention used (US or European) as it affects how the function treats end-of-month dates.
  • DAYS360 deals only with whole numbers and does not consider time within the day.
  • Ensure that start_date and end_date are recognized as valid dates; otherwise, the function will return a #VALUE! error.

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