WEEKSINYEAR in Collabora Office: Count ISO Weeks Without Confusing Calendar Dates
Use Collabora WEEKSINYEAR for 52- or 53-week calendars and distinguish a year’s week count from a date’s week number.
Verification status: See the evidence and test scope described in this guide. How formula examples are checked
Quick answer: =WEEKSINYEAR(DATE(2020;7;1)) has independently expected result 53; using a 2021 date targets 52. The function reports the number of weeks assigned to the date’s year under the documented ISO-style week rule.
Syntax and week assignment
=WEEKSINYEAR(Date)
Date is one valid date in the desired year. The Collabora reference specifies Monday as the first day of the week and assigns a week spanning two years to the year containing most of its days. Its example gives 53 for a February 1970 date.
The result is a yearly count, not the week number of the input date. A midyear date is useful when building a year table because it avoids visually confusing dates close to the week-year boundary.
Do not calculate this count by rounding DAYSINYEAR/7. Calendar years contain 365 or 366 days, while ISO week-year assignment includes whole weeks that can overlap neighboring calendar years.
Example 1: make a year-count table
Put years 2020, 2021, 2026 in A2:A4. In B2 enter =DATE(A2;7;1) and fill down. In C2 enter =WEEKSINYEAR(B2) and fill down.
Independent ISO-calendar targets are 53, 52, 53. A 53-week year occurs under the standard rule when January 1 is Thursday, or when a leap year begins on Wednesday. These conditions give a separate calendar-level check for the examples.
Label column C “Weeks in year.” Labeling it “Week number” would misrepresent the output and could lead someone to use it as a date-grouping key.
Example 2: compare day-count arithmetic
2020 has 366 days, and 366/7 is approximately 52.285714286. Its ISO week-year nevertheless has 53 assigned weeks. 2021 has 365 days, and 365/7 is approximately 52.142857143, while its assigned week count is 52.
The difference is a consequence of whole-week assignment at year boundaries. It does not mean extra days were added to the calendar year. A weekly plan must specify whether its rows follow ISO weeks or simply consecutive seven-day blocks starting January 1.
Advanced application: prepare a weekly planning template
For a selected year in B1, use =WEEKSINYEAR(DATE(B1;7;1)) as the expected number of ISO-week rows. Independently enumerate the week’s Monday dates in a calendar-aware planning table and compare its count.
Do not assume that January 1 is the first Monday or that week one lies wholly inside the calendar year. Some dates at the beginning or end of January/December belong to a neighboring ISO week-year. The yearly-count function does not produce those dates for you.
Advanced application: avoid a boundary-year mix-up
January 1, 2021 belongs to ISO week 53 of the 2020 week-year. That fact does not make the calendar year 2021 a 53-week ISO year. The independent expected WEEKSINYEAR result for a valid date in calendar year 2021 remains 52 under the function’s documented year selection.
Use an explicit year field and construct a midyear date for the count if your report separately stores ISO week-year identifiers. Do not feed an arbitrary boundary date and then assume its calendar year and ISO week-year are identical.
This boundary expectation is a model interpretation of the documented rule, not a captured native Collabora test. Verify it on the actual deployment before relying on a boundary-date import.
Errors and troubleshooting
Pass a real date, not a bare year number. Text parsing can depend on locale; the examples use DATE to avoid ambiguity. Format the result as a number.
If a 53rd planning row appears unexpectedly, check the selected year and the week-assignment convention. The help fixes Monday regardless of a different calendar display preference. Exact invalid-date errors and additional platform behavior remain unverified.
Availability, format and verification
Collabora Office 26.04 desktop help documents this exact function. The saved source was retrieved on 2026-10-13 and hash-verified for this guide on October 15, 2026. It identifies the namespace ORG.OPENOFFICE.WEEKSINYEAR and says the function is outside the cited OpenFormula 1.3 standard. This is not cross-product semantic certification.
The first introduced release and last functioning version are unknown. Online/mobile availability is not inferred. No native Collabora or WPS execution was performed. Results are independent calendar/string controls or explicitly identified documented examples. English names and semicolon separators are used.