WEEKS 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 arithmetic were checked.

WEEKS returns an integer interval between two dates. Mode 0 divides the elapsed day count by seven and truncates toward zero. Mode 1 uses a Monday-based calendar-week calculation, but its integer-division implementation has a New Year boundary limitation that matters for dates before the first Monday used by its calculation. Release implementation.

WEEKS(StartDate;EndDate;Mode)

• StartDate, EndDate: required date serials or date cells.
• Mode: required integer. Use 0 for complete seven-day intervals or 1 for the calendar calculation. The implementation treats other modes as the interval branch; this guide recommends the documented choices.
• All three arguments are required. Date inputs enter the add-in as integer serials.

The native column contains saved 4.1.16 results; independent references use high-precision arithmetic and the stated source rules. Values are shown to twelve decimal places where needed. Enter DATE expressions directly rather than locale-dependent date text.

The generated ODF uses ORG.OPENOFFICE.WEEKS, mapped to the English worksheet name WEEKS by the release function map. The saved operation was verified after recalculation.

January 1 to January 15, 2024 is 14 days, so Mode 0 gives 2. January 1 to January 14 is 13 days, so it gives 1. Reversing the 14-day interval gives −2. This is truncation toward zero, not rounding to the nearest week.

From Sunday January 7 to Monday January 8, 2024, Mode 0 gives 0 while Mode 1 gives 1. That pair crosses a Monday boundary even though only one day elapsed. Choose the definition before interpreting the result.

Calendar-mode limitation in the tested release: =WEEKS(DATE(2021;1;1);DATE(2021;1;4);1) returns 0, although the dates cross from Friday to the following Monday. The source subtracts a Monday anchor derived from January 4 and applies C++ integer division, which truncates a negative partial week toward zero. This is not a reliable general ISO week-boundary counter around that anchor.

For an explicitly Monday-based boundary count, enter =DATE(2021;1;1) in A2 and =DATE(2021;1;4) in B2. Then subtract the Monday at or before each date: =((B2-WEEKDAY(B2;2)+1)-(A2-WEEKDAY(A2;2)+1))/7. For January 1 to January 4, 2021, this calendar arithmetic gives 1. That alternative was independently calculated; it was not included in the native example fixture.

Use Mode 0 when whole elapsed weeks are the actual requirement. Its negative partial intervals truncate toward zero, so −6 days gives 0 weeks, not −1. For Mode 1, keep the demonstrated New Year limitation visible and verify boundary dates before using the function in a reporting calendar.

The eight native calls use valid ordinary dates and Modes 0 or 1. Text dates, missing inputs, extreme dates and other modes were not executed. The ODF stored the registered ORG.OPENOFFICE function identity; no manual-entry or other-locale behavior is inferred.

DATE, WEEKDAY, DAYS.

• 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, inputs 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.