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DAYS360 Function

Excel 2007+

Summary

The DAYS360 function calculates the number of days between two dates using a standardized 360-day year (12 months of 30 days each). This method is commonly used in financial and accounting calculations for loan interest, bond pricing, and payment schedules.

Syntax

DAYS360(start_date, end_date, [method])

Parameters

Parameter	Type	Required	Description
start_date	`Date`	Yes	Starting date. Dates can be entered as cell references, DATE function results, or direct date values.
end_date	`Date`	Yes	Ending date. Returns negative result if start_date is after end_date.
method	`Boolean`	No	Optional. FALSE=US/NASD method (default), TRUE=European method.

Using the DAYS360 Function

DAYS360 standardizes date differences to a 360-day year, making it perfect for financial calculations where actual calendar days would create inconsistencies. Use it for loan amortizations, bond interest calculations, and any accounting scenario requiring fixed 30-day months.

Common DAYS360 Examples

Basic U.S. Method Calculation

=DAYS360(DATE(2023,1,1),DATE(2023,12,31))

Calculates days between Jan 1 and Dec 31 using default U.S. method. Returns 360.

European Method Example

=DAYS360("1/31/2023","2/28/2023",TRUE)

Uses European method where 31st becomes 30th. Returns 28 days.

Negative Result Example

=DAYS360(DATE(2023,6,15),DATE(2023,3,15))

Start date after end date returns negative value: -90.

Frequently Asked Questions

DAYS360 returns a negative number indicating the dates are in reverse order.

U.S. method adjusts end dates differently when start is before 30th; European simply converts all 31sts to 30ths.

Yes, but ensure cells are properly formatted as dates, not text.

Common Errors and Solutions

#VALUE! Error

Cause: Dates entered as text instead of actual date values

Solution: Use DATE() function or ensure cells are formatted as dates

#NUM! Error

Cause: Invalid date values or non-numeric inputs

Solution: Verify both date parameters contain valid dates

Notes

Excel stores dates as serial numbers starting from January 1, 1900 = 1
Always use DATE function for clarity: DATE(year,month,day)
U.S. method is default and used by NASD (National Association of Securities Dealers)
Perfect companion to PMT, IPMT, and other financial functions

Compatibility

Available in: Excel 2007, Excel 2010, Excel 2013, Excel 2016, Excel 2019, Excel 2021, Excel 365

Not available in: Excel 2003, Excel XP, Excel 2000, Excel 97

Content last reviewed: December 9, 2025
Update frequency: As needed
Excel versions tested: Excel 2007+