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WEEKDAY Function (LibreOffice Calc)

Date & Time Intermediate LibreOffice Calc Introduction not established

The WEEKDAY function returns the day of the week for a given date, using one of several numbering systems. It is essential for scheduling, calendars, dashboards, and weekday-based logic.

Verification status: Consult the documentation, examples and any stated test scope below. How formula examples are checked

Availability and version history

  • Introduced: Documented by LibreOffice 26.8.1.1; original introduction not established.
  • Availability: Supported in LibreOffice 26.8.1.1, verified against its function registry. This identifies a supported release, not a final working version.
  • Scope: Desktop Calc, using the English function name. Availability in other spreadsheet applications is separate.
  • Checked: 2026-10-14 — function reference; versioned support. Documentation/source check; not a new native test. Existing example-specific test claims below retain their stated scope.
The **WEEKDAY** function returns the **day of the week** for a given date, using one of several numbering systems. It is highly flexible and ideal for scheduling logic, dashboards, calendars, and any workflow that depends on weekday behavior.

What the WEEKDAY Function Does

  • Returns the day of the week as a number
  • Supports multiple numbering systems
  • Works with real dates, serial numbers, and DATEVALUE
  • Ignores time components

It is designed to be flexible, locale‑aware, and ideal for weekday logic.

Syntax

WEEKDAY(date; [mode])

Arguments

  • date:
    A valid date or serial number.

  • mode (optional):
    Determines the numbering system.

Numbering Systems

Mode Meaning Week Starts On Returns
1 (default) Sunday = 1 Sunday 1–7
2 Monday = 1 Monday 1–7
3 Monday = 0 Monday 0–6

Notes:

  • Mode 2 is the most common for business logic.
  • Mode 3 is ideal for zero‑based indexing.

Basic Examples

Default behavior (Sunday = 1)

=WEEKDAY("2024-03-15")

Monday = 1

=WEEKDAY("2024-03-15"; 2)

Monday = 0 (zero‑based)

=WEEKDAY("2024-03-15"; 3)

Using a cell reference

=WEEKDAY(A1)

Weekday of today

=WEEKDAY(TODAY(); 2)

Advanced Examples

Convert weekday number to name

=TEXT(A1; "NNNN")

Check if a date is a weekend (Mode 2)

=WEEKDAY(A1;2)>5

Check if a date is a weekday

=WEEKDAY(A1;2)<=5

Get next Monday

=A1 + MOD(1 - WEEKDAY(A1;2); 7)

Get previous Monday

=A1 - MOD(WEEKDAY(A1;2)-1; 7)

Get next business day

=A1 + IF(WEEKDAY(A1;2)>=5; 8-WEEKDAY(A1;2); 1)

Extract weekday from text using DATEVALUE

=WEEKDAY(DATEVALUE(A1); 2)

Extract weekday from imported CSV timestamp

=WEEKDAY(DATEVALUE(LEFT(A1;10)); 2)

Extract weekday from Excel serial date stored as text

=WEEKDAY(DATE(1899;12;30)+VALUE(A1); 2)

Build a weekday label (e.g., “Mon”)

=TEXT(A1; "NNN")

Build a full weekday label (e.g., “Monday”)

=TEXT(A1; "NNNN")

Edge Cases and Behavior Details

WEEKDAY returns an integer (0–7 depending on mode)

Accepts:

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

Invalid text → Err:502

Time components are ignored

WEEKDAY may differ from ISOWEEKNUM

WEEKDAY of an error → error propagates

Zero‑based mode (3) is useful for indexing arrays

Common Errors and Fixes

Err:502 — Invalid argument

Cause:

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

Fix:

  • Wrap with DATEVALUE
  • Clean text with TRIM or SUBSTITUTE

Wrong weekday due to mode confusion

Fix:

  • Use mode 2 for Monday‑start logic
  • Use mode 3 for zero‑based indexing

Wrong result due to text dates

Fix:

  • Normalize with DATEVALUE

Best Practices

  • Use mode 2 (Monday = 1) for business logic
  • Use mode 3 (Monday = 0) for indexing
  • Normalize text dates with DATEVALUE
  • Use WEEKDAY with TEXT() to build labels
  • Use WEEKDAY for scheduling, calendars, and dashboards
WEEKDAY is your weekday‑logic engine — perfect for scheduling, dashboards, business rules, and calendar workflows.
  • Use ISOWEEKNUM for ISO‑8601 week numbering
  • Use WEEKNUM for locale‑specific week numbering
  • Use DATE for constructing comparison dates
  • Use DATEDIF and DAYS for interval calculations

By mastering WEEKDAY and its companion functions, you can build powerful, flexible, and fully dynamic weekday‑based workflows in LibreOffice Calc.

Reproducible example (tested in LibreOffice Calc)

This standalone example was calculated in LibreOffice Calc 25.2.3.2 and matched the expected value. It is a practical cross-check of one usage, not proof that every example elsewhere on this page is correct.

=WEEKDAY(DATE(2025;1;12);2)

Expected result: 7.

Number weekdays with Monday equal to 1.

If the result differs, check the referenced cells, argument separators and number formatting. For more information, consult the LibreOffice Calc official help.