What's the difference between DAYS360 and DAYS?

DAYS360 calculates days in a 360-day year system used by bond and mortgage markets (30 days per month), while DAYS counts actual calendar days. DAYS360 is rarely needed outside financial instruments with 360-day conventions.

Should I use DAYS360 for household budget calculations?

No. DAYS360 is designed for securities and financial markets. For household budgets, use DAYS() to count actual calendar days or DATEDIF() for more granular control over day counting.

How does the method parameter change DAYS360's behavior?

method=FALSE (US) treats day 31 as day 31, while method=TRUE (European) treats day 31 as day 30 for calculation purposes. This adjustment only matters when your dates fall on the 31st of any month.

Does DAYS360 work with times, or only dates?

DAYS360 ignores the time component entirely, working only with the date portion of date-time values. To include hours or minutes in your calculation, you'll need to use additional formulas or helper functions.

DAYS360 function

Returns the number of days between two dates using a 360-day year where each month equals 30 days, commonly used in financial calculations.

=DAYS360(start_date, end_date, [method])

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Arguments

How DAYS360 reads its arguments

Argument	Required	Description
start_date	Required	The date when the period begins; must be provided as a date value (not text) and earlier than end_date.
end_date	Required	The date when the period ends; treated as day 30 if falling on the 31st under European method only.
method	Optional	Optional logical value (FALSE or 0 = US method, TRUE or 1 = European); defaults to FALSE if omitted.

Returns

A number representing the count of days calculated in a 360-day year system.

Availability

Excel: All · Google Sheets: Supported

Worked examples

1. Calculate days in a single budget month

Category	Month	Start Date	End Date
Groceries	January	1/1/2024	1/31/2024

=DAYS360(DATE(2024,1,1), DATE(2024,1,31))

Result: 30

In a 360-day year convention, each month is assigned exactly 30 days regardless of actual calendar length. From January 1 to January 31, the 360-day calculation yields 30 days, representing one complete month in this financial system used primarily for bond and mortgage calculations.

2. Calculate days spanning multiple budget periods

Category	Budget Period	Start Date	End Date
Utilities	Jan through mid-Feb	1/1/2024	2/15/2024

=DAYS360(DATE(2024,1,1), DATE(2024,2,15))

Result: 44

Spanning January 1 to February 15 represents one complete month (30 days) in the 360-day system plus 14 additional days in February, totaling 44 days. This differs from DAYS() which would return 46 actual calendar days, highlighting why DAYS360 is specific to financial instruments.

3. Compare US and European 360-day calculation methods

Category	Comparison	Start Date	End Date	US Method	European Method
Entertainment	Month-end variance	1/15/2024	1/31/2024	FALSE	TRUE

=DAYS360(DATE(2024,1,15), DATE(2024,1,31), FALSE) vs =DAYS360(DATE(2024,1,15), DATE(2024,1,31), TRUE)

Result: 16 (US) vs 15 (European)

The US method (FALSE) counts January 31 as the actual day 31, producing a 16-day difference from the 15th. The European method (TRUE) treats any 31st as day 30 for calculation purposes, reducing the difference to 15 days. This distinction only affects calculations when dates fall on the 31st.

Common errors

Which DAYS360 error are you seeing?

Error	Why it happens	How to fix it
#NUM!	start_date is later than end_date, violating the required chronological order for the function.	Verify your dates are in correct order with start_date earlier than end_date. Check cell references if using indirect references.
#VALUE!	Dates are provided as text strings (e.g., "1/1/2024") instead of actual date values the spreadsheet recognizes.	Wrap text dates in DATEVALUE() function or construct them explicitly with DATE(year, month, day). Verify date cells contain formatted dates, not text.
#VALUE!	method parameter is set to a value other than 0, 1, FALSE, or TRUE (e.g., "US" or 2).	Set method to either FALSE (or 0) for US method or TRUE (or 1) for European method. Remove any text values for this parameter.

Tips and when to use something else

DAYS360 uses a 360-day convention (30 days per month), not actual calendar days—use DAYS() or DATEDIF() for real day counts in household budgets.
DAYS360 exists primarily for securities and bond markets; for household budget calculations, DAYS() or DATEDIF() are typically more appropriate and intuitive.
The method parameter only affects dates falling on the 31st; for all other dates, both US and European methods return identical results.
When comparing two dates on the same day, DAYS360 returns 0, making it useful for verifying date equality or identity checks in formulas.

Related functions

DAYSDAYS returns the number of calendar days between two dates, with positive or negative result depending on date order.DATEDIFReturns the number of time units (days, months, years) between two dates, useful for calculating durations, aging, or time-to-deadline.DATEDATE returns a date serial number from year, month, and day arguments, enabling date construction from separate numeric components.DATEVALUEDATEVALUE converts text strings representing dates into serial numbers Excel and Sheets recognize, enabling date calculations and sorting.EDATEReturns a date that is a specified number of months before or after a start date, making it easy to calculate contract expirations and probation deadlines.

Frequently asked questions

What's the difference between DAYS360 and DAYS?: DAYS360 calculates days in a 360-day year system used by bond and mortgage markets (30 days per month), while DAYS counts actual calendar days. DAYS360 is rarely needed outside financial instruments with 360-day conventions.
Should I use DAYS360 for household budget calculations?: No. DAYS360 is designed for securities and financial markets. For household budgets, use DAYS() to count actual calendar days or DATEDIF() for more granular control over day counting.
How does the method parameter change DAYS360's behavior?: method=FALSE (US) treats day 31 as day 31, while method=TRUE (European) treats day 31 as day 30 for calculation purposes. This adjustment only matters when your dates fall on the 31st of any month.
Does DAYS360 work with times, or only dates?: DAYS360 ignores the time component entirely, working only with the date portion of date-time values. To include hours or minutes in your calculation, you'll need to use additional formulas or helper functions.

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Reviewed 2026-09-17