WEEKSINYEAR in Calligra Sheets: 52 or 53 ISO Weeks

=WEEKSINYEAR(2026) has an independently calculated, source-supported expected result of 53, while =WEEKSINYEAR(2024) has an expected result of 52. This function takes the calendar year as an integer and returns the count of ISO-numbered weeks that belong to that year. KDE’s handbook explicitly documents WEEKSINYEAR(year), and Calligra 26.08.2 source uses Qt’s ISO week-number calculation around December 31. No output was observed in a running Calligra application. [E1][E2][E3][E5]

Use this function when building annual calendars, week-based dashboards, or reports that must accommodate week 53. A year with 366 days can still have just 52 ISO weeks; leap-day status is a different measurement. [E3][E5]

=WEEKSINYEAR(year)

The function returns an integer: typically 52 or 53 for ordinary valid Gregorian years. The official handbook/XML lists one parameter and no optional arguments/defaults. The pinned source registers the alternate interoperability name COM.SUN.STAR.SHEET.ADDIN.DATEFUNCTIONS.GETWEEKSINYEAR; that long identifier is an alias, not another function. [E1][E2][E3]

ISO week-year convention: Weeks begin Monday; week 1 is the week containing the year’s first Thursday. The Calligra source examines December 31 and, if Qt assigns that date to the following ISO week-year, examines the week seven days earlier. It thereby obtains the last numbered ISO week of the specified year. This code-level procedure, not another spreadsheet’s behavior, supports the results below. [E3][E5]

Because this is a single-argument function, it does not use a separator itself. Combined examples below use semicolons, matching KDE’s English handbook. A localized installation may have different separators/decimal entry conventions; verify via the installed function insertion dialog. [E1][E7]

On a blank sheet label A1 Year, B1 ISO weeks, C1 Calendar days, D1 Week-53 flag. Enter year values in A2:A9 as numeric whole years. Put the formulas shown in row 2 and copy down:

B2: =WEEKSINYEAR(A2)
C2: =IF(ISLEAPYEAR(A2);366;365)
D2: =IF(B2=53;"Extra week";"Standard year")

How results were checked: The B outputs were independently calculated using ISO week numbering for each specified year, with an additional source-logic calculation of Qt QDate(year,12,31).weekNumber(&yearNumber) and its seven-day correction. The C/D columns follow the Gregorian leap-year rule and the documented Calligra IF and ISLEAPYEAR syntax. No native Calligra calculation, screenshot, workbook-import comparison or output observation has occurred. [E1][E3][E5]

Why 2015 and 2026 differ from 2024: January 1, 2015 and January 1, 2026 are Thursdays, so their first ISO week starts in the preceding December and the final ISO week is week 53. The 2024 leap year still has 52 ISO weeks. This is a reproducible annual scheduling edge case, not a claim that every leap year has 53 ISO weeks. [E3][E5]

Put a reporting year in F2 (for example 2026 as an integer). Use this expected-output formula in G2:

=IF(WEEKSINYEAR(F2)=53;"Include week 53";"Weeks 1–52")

For F2=2026, the independently expected text is Include week 53. For F2=2024, it is Weeks 1–52. A purely numerical alternative is =WEEKSINYEAR(F2)*7, giving 371 and 364 calendar days in complete ISO weeks respectively. This is not the number of days in the calendar year; those weeks can extend into adjacent years. The formulas are reasoned from the source algorithm, not observed in Calligra. [E3][E5]

For a date-based workflow, the extra conversion must be explicit:

=WEEKSINYEAR(YEAR(DATE(2026;7;1)))

The source-inferred expected result is 53; YEAR extracts the calendar year from the created date, then WEEKSINYEAR operates on that year. This example uses separately registered DATE and YEAR and remains untested in a running application. It is not equivalent to passing a date serial directly to WEEKSINYEAR. [E2][E3]

• Passing a date instead of a year: In Calligra, WEEKSINYEAR(2026) and WEEKSINYEAR(DATE(2026;1;1)) should not be assumed equivalent. The code converts its argument to an integer year; the date serial can represent a completely different number. Convert a date with YEAR(date) where required. [E1][E3]
• Confusing week count with a date’s week number: WEEKSINYEAR(2026) describes an entire ISO week-year’s number of weeks. WEEKNUM(date;method) and ISOWEEKNUM(date) instead determine a particular date’s week; they should not be interchanged. A separate source/documentation discrepancy affects Calligra’s ISOWEEKNUM at year boundaries and requires native validation; do not assume a chained formula is equivalent without testing. [E3][E5][E8]
• Assuming all leap years have 53 weeks: Year 2024 has 366 days but 52 ISO weeks; year 2026 has 365 days and 53 ISO weeks. [E5]
• Invalid or unusual year input: The examined implementation obtains an integer and constructs Qt QDate(year,12,31). Invalid years, quoted text, decimals and blank cells were not natively tested. Do not promise a particular error string, rounded value or coercion behavior. Use validated, positive whole-number years. [E3]
• Function not found or wrong separator: Check spelling WEEKSINYEAR, the leading equals sign, and installed version; registration in the 26.08.2 source does not guarantee every installed edition/platform enables it. The multi-argument IF examples use semicolons as KDE documents. [E1][E2][E4][E7]

Calligra Sheets 26.08.2: The official function signature is WEEKSINYEAR(year), where year is an integer. Source code confirms Qt ISO week-number logic and an alternate dotted registration. Outputs here are independently calculated and native-untested. [E1][E2][E3]

Apache OpenOffice Calc: The official Apache help page documents WEEKSINYEAR(date), where the argument is a date and the function requires an Analysis AddIn in that documented edition. It expressly states the function is not portable to Excel. This is a critical parameter difference: copying WEEKSINYEAR(A2) between Calligra and Apache Calc may silently change meaning if A2 is an integer year. Convert or rewrite intentionally, then test. [E6]

Microsoft Excel: Microsoft’s official ISOWEEKNUM(date) documentation returns an ISO week number for a date, not an entire year’s 52/53 week count. Apache’s official portability note says WEEKSINYEAR is not an Excel function. For a valid reporting year Y, the independently reasoned concept ISOWEEKNUM(DATE(Y,12,28)) evaluates the final ISO week of that year in Excel, but syntax, dates and return values in an Excel workbook must be checked there; it is not evidence of Calligra’s execution. [E5][E6][E9]

• Calligra ISLEAPYEAR guide — comparison of calendar days and ISO weeks.
• Calligra WEEKNUM guide — week number for a date.
• KDE Calligra function handbook — WEEKSINYEAR(year) type, single parameter and WEEKSINYEAR(2000) → 52; accessed 2026-10-12. [E1]
• Calligra 26.08.2 registry and WEEKSINYEAR implementation — pinned commit, accessed 2026-10-12. [E2][E3]
• KDE latest release listing — 26.08.2 dated 2026-10-08; accessed 2026-10-12. [E4]
• Apache OpenOffice WEEKSINYEAR documentation — date parameter/add-in and non-Excel portability; accessed 2026-10-12. [E6]
• Microsoft Excel ISOWEEKNUM documentation — date-to-week-number behavior for comparison only; accessed 2026-10-12. [E9]

Validation: Official documentation and pinned source reviewed; example values independently calculated. Native Calligra execution was not performed.