DAYS360 in Collabora Office: Count Interest Days on a 360-Day Year
Use Collabora DAYS360 with explicit US or European conventions, distinguish interest days from calendar days, and audit a simple accrual schedule.
Verification status: See the evidence and test scope described in this guide. How formula examples are checked
Quick answer: =DAYS360(DATE(2026;1;15);DATE(2026;7;15);0) has an independently expected result of 180. It counts days using a 360-day interest-year convention, rather than the actual number of elapsed calendar days.
Syntax and method selection
=DAYS360(Date1; Date2 [; Type])
Date1 and Date2 are required date values. Type is optional:
- 0 or omitted: the US NASD method.
- Any nonzero Type: the European method.
The vendor states that a Date2 earlier than Date1 produces a negative result. Type selects a day-count convention; it is not a number of decimal places, a holiday flag, or a request for actual calendar days.
Use DATE to create inputs, or references to numeric date cells. A bare expression such as 2026-1-15 is subtraction, not a date. The help also describes quoted ISO dates, but their text conversion can depend on detailed calculation settings. DATE avoids that text-conversion dependency.
Example: compare equal monthly positions
Enter these formulas as date values in A2:B4. In C2 enter =DAYS360(A2;B2;0) and fill down.
| Row | A: start | B: end | C: independent interest days |
|---|---|---|---|
| 2 | =DATE(2026;1;15) |
=DATE(2026;2;15) |
30 |
| 3 | =DATE(2026;1;15) |
=DATE(2026;7;15) |
180 |
| 4 | =DATE(2026;7;15) |
=DATE(2026;1;15) |
−180 |
In D2 use =B2-A2 and fill down. The independent actual-calendar results are 31, 181, and −181. The difference is intentional: the two columns answer different questions.
For these ordinary mid-month dates, replacing Type 0 with Type 1 gives the same 30/360 results. This agreement does not mean the two conventions always agree. Month-end adjustments are exactly where choosing the proper convention matters.
Advanced example: audit a simple interest accrual
For a hypothetical principal of 12000 and annual simple rate 6%, use the January 15 to July 15 row:
=12000*6%*C3/360
The independently expected amount is 360: 12000×0.06×180/360. Label the amount with the chosen “US NASD 30/360” basis so the worksheet does not hide its convention.
For comparison, actual days divided by 365 would give =12000*6%*(B3-A3)/365, approximately 357.04109589. That is a different model, not a correction to the DAYS360 result. Use whichever basis the underlying calculation requires; this example does not choose a contract’s day-count terms.
Advanced example: reconcile a monthly schedule
Enter start dates for January 15, February 15, and March 15, 2026, with matching end dates one month later. Each interval has an independent 30/360 count of 30. The total is 90, matching January 15 to April 15 under this regular-date example.
This is a useful audit pattern: store the actual boundary dates, calculate each interval, then compare the sum with the whole interval. Avoid assuming the same reconciliation holds under every unusual month-end convention without checking the relevant rules and target application.
Month-end limitations and troubleshooting
The dedicated Collabora section identifies US NASD and European methods but does not spell out every February, leap-year, or end-of-month adjustment. This guide therefore uses unambiguous mid-month controls and does not import another program’s boundary algorithm as a verified Collabora contract.
If a workbook differs by one or two days, inspect the exact dates, Type, and month-end convention before changing arithmetic. A correct result under a different convention can still be wrong for your purpose. Reversed dates explain negative results; date-looking text can explain parsing or value errors.
The help discusses a text-to-number setting associated with #VALUE! during date conversion. Prefer converting source dates deliberately rather than changing a workbook-wide setting solely to hide one error. Native invalid-input codes beyond the documented guidance are not certified here.
File-format scope
The vendor identifies DAYS360 as part of OpenDocument 1.2. That standards statement is separate from the first Collabora release to support it and does not certify interoperability with another spreadsheet engine.
Availability and verification
The exact function is documented in Collabora Office 26.04 desktop help, retrieved and reviewed on October 17, 2026. This establishes a documentation scope, not the first release that introduced the function or the last version in which it works; those versions and any retirement date remain unestablished. Collabora Online and mobile support are not inferred from desktop help, nor is behavior in another spreadsheet product.
The examples are documentation-based expectations with independent calculations. They have not been executed in Collabora Office. No application screenshot or native error/coercion certification is implied. Formulas use English function names and semicolon argument separators.
References
- Collabora Office 26.04: DAYS360 (checked October 17, 2026).
- Editorial testing standards.