WEEKDAY

Quirk found

Category: Date and time · Last tested 2026-09-01

Real compatibility results for the WEEKDAY function: executed in Excel for the web, Google Sheets and LibreOffice Calc, with desktop Excel behavior from Microsoft’s official documentation (we do not run desktop Excel — Excel for the web is a different application and is executed separately). Syntax and links to that documentation are below.

Support matrix

Engine	Documented	Live-tested	Verdict
Excel (desktop)	Yes	No — documented only	n/a
Excel for the web	—	Yes (recalc, 2026-09-01)	Supported, behaves as documented
Google Sheets	Yes	Yes (Drive import, 2026-08-29)	Supported, behaves as documented
LibreOffice Calc	Yes	Yes (25.8.7.3, 2026-07-29)	Quirk found

LibreOffice version history

We executed the same test cases under each LibreOffice release to show exactly when WEEKDAY’s support changed — not documentation claims, real results.

LibreOffice version	Verdict	Tested
24.2.0.3	Quirk found	2026-08-29
24.8.7.2	Quirk found	2026-08-29
25.2.0.3	Quirk found	2026-08-29
25.8.7.3	Quirk found	2026-07-29

Why isn't WEEKDAY working in LibreOffice?

WEEKDAY exists in LibreOffice 25.8.7.3, but it is not a drop-in match for Excel — our executed tests found real behavioral differences (detailed in the test results on this page). If a formula that works in Excel or Google Sheets misbehaves in LibreOffice, compare your usage against the failing cases above before assuming your data is wrong.

Discovered quirks

=WEEKDAY(DATE(2008,2,14),99) on LibreOffice Calc returned #VALUE!, but the documented/expected result is #NUM!.
Provenance
Microsoft docs: an invalid return_type raises #NUM!.; MISMATCH vs expected: expected '#NUM!', got '#VALUE!'

Executed test cases

Excel for the web (executed 2026-09-01 via OneDrive recalculation)

These values come from Excel for the web, not from desktop Excel. They are two different implementations of the calculation engine, and this run measured only the web one: the corpus was uploaded to OneDrive as .xlsx, recalculated by Excel for the web on open, and downloaded again for readback. Excel for the web is a rolling service with no pinnable version, so the run is identified by its date. Where a value here disagrees with the Expected column — which is Microsoft’s documentation of the desktop product — we cannot tell you whether the web engine diverges from the desktop one or the documentation is wrong about both, because we do not run desktop Excel.

Formula	Description	Result	Expected	Verdict
=WEEKDAY(DATE(2008,2,14))	Default return_type 1: Sunday=1..Saturday=7. Feb 14, 2008 is a Thursday. Source: https://support.microsoft.com/en-us/office/weekday-function-60e44483-2ed1-439f-8bd0-e404c190949a (worked example, WEEKDAY(A2)=5)	5	5	Matched
=WEEKDAY(DATE(2008,2,14),2)	return_type 2: Monday=1..Sunday=7. Source: Microsoft WEEKDAY docs worked example, WEEKDAY(A2,2)=4.	4	4	Matched
=WEEKDAY(DATE(2008,2,14),3)	return_type 3: Monday=0..Sunday=6 (zero-based). Thursday is 3 in this scheme.	3	3 Provenance Per Microsoft's return_type table, mode 3 maps Monday..Sunday to 0..6; Thursday (the 4th weekday counting Monday=0) = 3.	Matched
=WEEKDAY(DATE(2008,2,14),12)	return_type 12: Tuesday=1..Monday=7 (ISO-style variant start day). Thursday is the 3rd day in this scheme.	3	3 Provenance Per Microsoft's return_type table, mode 12 maps Tuesday=1,Wed=2,Thu=3,...,Monday=7.	Matched
=WEEKDAY(DATE(2008,2,14),16)	return_type 16: Saturday=1..Friday=7. Thursday is the 6th day in this scheme.	6	6 Provenance Per Microsoft's return_type table, mode 16 maps Saturday=1,Sun=2,Mon=3,Tue=4,Wed=5,Thu=6,Fri=7.	Matched
=WEEKDAY(DATE(2008,2,14),99)	An out-of-range return_type (not one of the documented 1,2,3,11-17 values) is a documented error condition.	#NUM!	#NUM! Provenance Microsoft docs: an invalid return_type raises #NUM!.	Matched

Google Sheets (executed 2026-08-29 via Drive import)

Google Sheets is a rolling service with no pinnable version, so this run is identified by its date. The corpus was imported to Drive as .xlsx, recalculated by Sheets, and exported back for readback.

Formula	Description	Result	Expected	Verdict
=WEEKDAY(DATE(2008,2,14))	Default return_type 1: Sunday=1..Saturday=7. Feb 14, 2008 is a Thursday. Source: https://support.microsoft.com/en-us/office/weekday-function-60e44483-2ed1-439f-8bd0-e404c190949a (worked example, WEEKDAY(A2)=5)	5	5	Matched
=WEEKDAY(DATE(2008,2,14),2)	return_type 2: Monday=1..Sunday=7. Source: Microsoft WEEKDAY docs worked example, WEEKDAY(A2,2)=4.	4	4	Matched
=WEEKDAY(DATE(2008,2,14),3)	return_type 3: Monday=0..Sunday=6 (zero-based). Thursday is 3 in this scheme.	3	3 Provenance Per Microsoft's return_type table, mode 3 maps Monday..Sunday to 0..6; Thursday (the 4th weekday counting Monday=0) = 3.	Matched
=WEEKDAY(DATE(2008,2,14),12)	return_type 12: Tuesday=1..Monday=7 (ISO-style variant start day). Thursday is the 3rd day in this scheme.	3	3 Provenance Per Microsoft's return_type table, mode 12 maps Tuesday=1,Wed=2,Thu=3,...,Monday=7.	Matched
=WEEKDAY(DATE(2008,2,14),16)	return_type 16: Saturday=1..Friday=7. Thursday is the 6th day in this scheme.	6	6 Provenance Per Microsoft's return_type table, mode 16 maps Saturday=1,Sun=2,Mon=3,Tue=4,Wed=5,Thu=6,Fri=7.	Matched
=WEEKDAY(DATE(2008,2,14),99)	An out-of-range return_type (not one of the documented 1,2,3,11-17 values) is a documented error condition.	#NUM!	#NUM! Provenance Microsoft docs: an invalid return_type raises #NUM!.	Matched

LibreOffice Calc 25.8.7.3 (tested 2026-07-29)

Formula	Description	Result	Expected	Verdict
=WEEKDAY(DATE(2008,2,14))	Default return_type 1: Sunday=1..Saturday=7. Feb 14, 2008 is a Thursday. Source: https://support.microsoft.com/en-us/office/weekday-function-60e44483-2ed1-439f-8bd0-e404c190949a (worked example, WEEKDAY(A2)=5)	5	5	Matched
=WEEKDAY(DATE(2008,2,14),2)	return_type 2: Monday=1..Sunday=7. Source: Microsoft WEEKDAY docs worked example, WEEKDAY(A2,2)=4.	4	4	Matched
=WEEKDAY(DATE(2008,2,14),3)	return_type 3: Monday=0..Sunday=6 (zero-based). Thursday is 3 in this scheme.	3	3 Provenance Per Microsoft's return_type table, mode 3 maps Monday..Sunday to 0..6; Thursday (the 4th weekday counting Monday=0) = 3.	Matched
=WEEKDAY(DATE(2008,2,14),12)	return_type 12: Tuesday=1..Monday=7 (ISO-style variant start day). Thursday is the 3rd day in this scheme.	3	3 Provenance Per Microsoft's return_type table, mode 12 maps Tuesday=1,Wed=2,Thu=3,...,Monday=7.	Matched
=WEEKDAY(DATE(2008,2,14),16)	return_type 16: Saturday=1..Friday=7. Thursday is the 6th day in this scheme.	6	6 Provenance Per Microsoft's return_type table, mode 16 maps Saturday=1,Sun=2,Mon=3,Tue=4,Wed=5,Thu=6,Fri=7.	Matched
=WEEKDAY(DATE(2008,2,14),99)	An out-of-range return_type (not one of the documented 1,2,3,11-17 values) is a documented error condition.	#VALUE!	#NUM! Provenance Microsoft docs: an invalid return_type raises #NUM!.	Mismatch

Docs & syntax

Excel (desktop): official documentation
Google Sheets: official documentation
LibreOffice Calc: official documentation

Related how-to recipes

Where WEEKDAY behaves differently

Every error code LibreOffice reports as #VALUE!
Across our 2,334-case executed corpus, 272 cases in 135 functions return #VALUE! in LibreOffice Calc 25.8.7.3 where Microsoft documents #NUM! (244), #N/A (15), #DIV/0! (10) or #REF! (3). Google Sheets returns the documented code on 239 of the 249 it has a function for. Identical in all four LibreOffice builds tested.
#NUM! vs #VALUE!: Excel vs LibreOffice
Domain errors Microsoft documents as #NUM! - LN(0), SQRT(-16), out-of-range LARGE - return #VALUE! in LibreOffice. Google Sheets returns #NUM! on all 16, executed: LibreOffice is alone.