DAYS360 Function (OpenOffice Calc)

• Introduced: First release not established; documented by OpenOffice.org 3.3.
• Supported in: Apache OpenOffice 4.1.16; this is a verified release, not a final supported version.
• Scope: Desktop Calc, English function names and semicolon-separated formulas.
• Checked: October 14, 2026. Eight ordinary reference formulas were recalculated from generated ODF in 4.1.16 on Linux x86-64, Build 9816. Source and independent calendar arithmetic were checked.

DAYS360 returns a synthetic day count based on twelve 30-day months. It is intended for a specified day-count convention, not the actual elapsed number of days. Its argument order is StartDate then EndDate, unlike DAYS(EndDate;StartDate). Release implementation.

DAYS360(StartDate;EndDate[;Type])

• StartDate, EndDate: required date serials or date cells. Time fractions are floored before calendar extraction in the pinned implementation.
• Type: optional logical selector. Omitted or FALSE uses the US method; TRUE uses the European method. Use 0 or 1 explicitly when exchanging workbooks.
• Square brackets indicate the optional argument and are not typed.

The native column contains saved 4.1.16 results; independent references use exact date arithmetic or rational fractions. Numerical values are shown to twelve decimal places where needed. Enter the DATE expressions directly rather than substituting locale-dependent text.

From February 29 to March 31, 2024, =DAYS360(DATE(2024;2;29);DATE(2024;3;31)) gives 30 under the default US method. Adding ;1 gives 31 under the European method. Actual elapsed days are 31. These are different conventions, so select the method required by the calculation rather than whichever number looks more plausible.

From January 31 to February 29, the default result is 29. The US start-date adjustment does not turn every end-of-February endpoint into day 30.

For the US branch, a starting day 31 becomes 30, and the last day of February also becomes 30. An ending day 31 becomes 30 when the adjusted starting day is 30. The European branch changes a day 31 to 30 at either end. The result is 360*(end_year-start_year)+30*(end_month-start_month)+end_day-start_day after those adjustments.

Do not assume the US result changes only its sign when you reverse dates. February 2, 1999 to March 31, 2000 gives 419, but the reversed default call gives −418. The current release body deliberately leaves the US endpoints in their supplied order. Its older introductory source comment describes earlier reversal behavior; the executable branch and saved results take precedence. The European branch swaps reversed dates and applies a negative sign.

Use actual date inputs and keep the convention visible in the worksheet. The European result for March 31, 2000 back to February 2, 1999 is −418; this does not make the default forward result 418. Avoid applying an external sign change to an already signed result.

Only the listed valid dates and Type choices were executed. Nonnumeric Type values, text dates and extreme dates are outside this evidence. A 30/360 result divided by 360 is meaningful only when that exact convention is appropriate for the model.

DATE, DAYS, YEARFRAC.

• Function-specific release implementation

The generated ODF produced the informational load warning “Not all attributes could be read.” The sheet was hard-recalculated and saved separately. All eight ordinary function identities and results were reconciled; a stale SUM cache changed from 999999 to 3 and an uncached SUM returned 7. This establishes the stated examples, not every workbook style or invalid input. Other explanatory identities are independent calculations. The authoring-tool XLSX was not executed in OpenOffice, and its preview values are not the native results reported here.