DAYS Function in ONLYOFFICE: Date Difference, Negative Results and Leap Years

DAYS(end_date,start_date) calculates the number of calendar days between two dates. The order is easy to reverse: the ending date comes first. To find the signed distance between 1 March and 28 February in a leap year, enter:

=DAYS(DATE(2024,3,1),DATE(2024,2,28))

Independently expected result: 2 (2024 has 29 February). Reversing the arguments is expected to produce −2, not an absolute value. The ONLYOFFICE DAYS function documentation confirms the argument order; the numeric outcomes are independently calculated predictions and were not observed in ONLYOFFICE.

=DAYS(end_date, start_date)

Neither parameter is optional. In the English help they are written in this order; commas separate the two arguments. The official ONLYOFFICE page describes dates but does not specify invalid input coercion, detailed time-of-day truncation, exact error-code outcomes, or minimum supported edition. In particular, the comprehensive text-date parsing and #VALUE!/#NUM! rules in Excel’s DAYS documentation are not automatically verified for ONLYOFFICE.

Enter headers in A1:D1: End date, Start date, DAYS result, Comment. Enter A2:B12 as the DATE(...) expressions below rather than importing localized date strings. In C2 type =DAYS(A2,B2) and fill through C12. Set C2:C12 to Number/General to avoid displaying integer differences as dates.

Every expected C-column value was computed using Python’s standard-library datetime.date subtraction; the provided CSV repeats the dates and expected outcomes. No ONLYOFFICE output was observed. DAY counts here refer to elapsed calendar-day boundaries, not business days: a weekend still contributes to a signed date difference.

1. Invoice aging. Assume A2 holds a due date, and B1 holds a dated reporting snapshot. =DAYS($B$1,A2) gives days past due when positive and days remaining when negative. If A2 is 2026-10-01 and B1 is 2026-10-11, independently expect 10 overdue days. To avoid losing sign, don’t wrap the result in ABS unless that is intentionally your business rule.

2. A rolling countdown. =DAYS(DATE(2026,12,31),TODAY()) means year-end date minus current date. If calculation occurs on an illustrative 2026-10-11, independently expect 81; on any later day the expected value differs. TODAY’s result and clock source were not natively tested. For stable testing, substitute =DATE(2026,10,11) for TODAY().

3. Days from first to last activity. If A2 is a start date and B2 is an end date, =DAYS(B2,A2) is an elapsed span. If the business wants to count both start and end calendar dates as inclusive days, use =DAYS(B2,A2)+1 only when end is not before start. Explain whether inclusive counting is actually required.

4. Overdue label. If A2 is a due date and B1 is a fixed report date: =IF(A2="","",IF(DAYS($B$1,A2)>0,"Overdue","Not overdue")). This treats a due date today as not overdue and preserves an empty date row. Validate how your imported workbook represents blanks.

5. Calculate a date interval before grouping by months. =DAYS(DATE(2024,3,1),DATE(2024,2,28)) is 2, not “one month”. DAYS gives calendar-day differences, while MONTH and YEAR extract components. It does not return complete months or fractional years.

6. Business-day exception. To count weekdays while excluding Saturday and Sunday, consider the separately documented NETWORKDAYS, not DAYS. Never label DAYS output as “working days” without adjusting for weekends, holidays and the approved work calendar.

Excel’s DAYS page has the same named arguments and order. It additionally gives specific behaviour for text inputs, numeric dates, and invalid data, but those implementation details were not tested against ONLYOFFICE. The ONLYOFFICE reference does not name versions or release minimums; the Desktop and Docs release streams are distinct. Date serial representations may differ under the documented 1904 setting. Portable examples in this guide use explicit DATE(...) arguments and the common interval definition rather than fragile regional text date literals.

The Insert Functions guide documents English formula examples with an = prefix, function names and commas between arguments. The Advanced Settings guide documents Formula Language, Region, and a workbook 1904 date system option. If your interface uses another formula language or locale, check the actual function picker and pasted formula separators; do not assume the English spelling/display carries over. The 1904 system can change underlying date serials when transferring files; prefer DATE(year,month,day) for explicit-date examples, and verify workbook settings when importing.

• DATE: construct unambiguous date inputs.

• TODAY: current date for rolling differences.

• NETWORKDAYS: working days, weekends and holidays.

• DAY and YEAR: date components, not elapsed days.

• DAYS

• ONLYOFFICE Spreadsheet Editor — function documentation
• NETWORKDAYS
• Desktop Editors changelog
• Docs 10.0 announcement
• Insert Functions guide
• Advanced Settings guide
• DATE

Verification status: Official documentation checked; example outcomes were independently reasoned or arithmetically checked where applicable. Not executed in ONLYOFFICE Spreadsheet Editor.

• No genuine ONLYOFFICE Spreadsheet Editor screenshots are included; this guide does not use mock application images.