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WEEKS Function (LibreOffice Calc)

Date & Time Intermediate LibreOffice Calc LibreOffice 3.5

The WEEKS function returns the number of whole weeks between two dates. It is essential for scheduling, reporting, HR calculations, project management, and any workflow requiring week-based intervals.

Verification status: Consult the documentation and examples below. Native application testing has not been documented for this guide. How formula examples are checked

The **WEEKS** function returns the **number of whole weeks** between two dates. It is ideal for scheduling, reporting, HR calculations, project management, and any workflow where week-based intervals matter. WEEKS works with real dates, serial numbers, and text converted with DATEVALUE.

What the WEEKS Function Does

  • Returns the whole number of weeks between two dates
  • Accepts dates, datetimes, and serial numbers
  • Can return positive or negative values
  • Ignores partial weeks unless mode = 1

It is designed to be simple, predictable, and ideal for week‑interval calculations.

Syntax

WEEKS(start_date; end_date; [mode])

Arguments

  • start_date:
    The beginning date.

  • end_date:
    The ending date.

  • mode (optional):

    • 0 (default): Count whole weeks only
    • 1: Count partial weeks as whole weeks (ceiling behavior)

Basic Examples

Whole weeks between two dates

=WEEKS("2024-01-01"; "2024-02-01")

Returns 4.

Weeks between dates with partial week ignored

=WEEKS("2024-01-10"; "2024-02-01")

Returns 3.

Weeks between dates counting partial weeks

=WEEKS("2024-01-10"; "2024-02-01"; 1)

Returns 4.

Using cell references

=WEEKS(A1; B1)

Advanced Examples

Weeks between today and a deadline

=WEEKS(TODAY(); A1)

Weeks between two text dates

=WEEKS(DATEVALUE(A1); DATEVALUE(B1))

Weeks between imported CSV timestamps

=WEEKS(DATEVALUE(LEFT(A1;10)); DATEVALUE(LEFT(B1;10)))

Weeks between Excel serial dates stored as text

=WEEKS(DATE(1899;12;30)+VALUE(A1); DATE(1899;12;30)+VALUE(B1))

Determine if two dates fall in the same week (7‑day block)

=WEEKS(A1; B1) = 0

Calculate weekly billing cycles

=BaseRate * WEEKS(StartDate; EndDate)

Calculate age in weeks

=WEEKS(A1; TODAY())

Weeks remaining in the year

=WEEKS(TODAY(); DATE(YEAR(TODAY());12;31))

Edge Cases and Behavior Details

WEEKS returns an integer

Accepts:

  • Real dates
  • Serial numbers
  • DATEVALUE outputs
  • ISO date strings

Invalid text → Err:502

Behavior details

  • Partial weeks ignored unless mode = 1
  • Negative results allowed
  • Time components ignored
  • Date order does not matter (Calc swaps automatically)

WEEKS of an error → error propagates

Common Errors and Fixes

Err:502 — Invalid argument

Cause:

  • Text not recognized as a date
  • Non-numeric values
  • Wrong separators

Fix:

  • Wrap with DATEVALUE
  • Clean text with TRIM or SUBSTITUTE

Wrong week count due to partial week

Fix:

  • Use mode = 1 to count partial weeks

Unexpected result from serial numbers

Cause:

  • Imported values represent days since epoch

Fix:

  • Convert with DATE(1899;12;30)+VALUE(A1)

Best Practices

  • Use WEEKS for scheduling, reporting, and project timelines
  • Normalize text dates with DATEVALUE
  • Use mode = 1 when partial weeks should count
  • Use WEEKS with NETWORKDAYS for business‑day logic
  • Use WEEKS for weekly reporting periods
WEEKS is your week‑interval engine — perfect for scheduling, reporting, HR logic, and any workflow where week‑based differences matter.
  • Use DAYS for day intervals
  • Use MONTHS for month intervals
  • Use YEARS for year intervals
  • Use DATEDIF for flexible interval logic
  • Use WEEKNUM or ISOWEEKNUM for week numbering
  • Use DATEVALUE for text conversion

By mastering WEEKS and its companion functions, you can build powerful, reliable, and fully structured week‑interval workflows in LibreOffice Calc.