DAYS

Supported, behaves as documented

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

Real compatibility results for the DAYS 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)	Supported, behaves as documented

LibreOffice version history

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

LibreOffice version	Verdict	Tested
24.2.0.3	Supported, behaves as documented	2026-08-29
24.8.7.2	Supported, behaves as documented	2026-08-29
25.2.0.3	Supported, behaves as documented	2026-08-29
25.8.7.3	Supported, behaves as documented	2026-07-29

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
=DAYS(DATE(2024,3,15),DATE(2024,3,1))	DAYS takes END_DATE FIRST, then start_date -- the opposite argument order from DAYS360/YEARFRAC. Verified via https://support.microsoft.com/en-us/office/days-function-57740535-d549-4395-8728-0f07bff0b9df ("DAYS(end_date, start_date)")	14	14 Provenance 2024-03-15 minus 2024-03-01 = 14 days	Matched
=DAYS(DATE(2024,3,1),DATE(2024,3,15))	Swapping which date is passed first (now the earlier date is 'end_date') flips the sign -- reinforcing that argument order is significant and not auto-corrected	-14	-14 Provenance Same two dates as DAYS_basic_end_first_argument_order but with roles swapped -> -14	Matched
=DAYS("15-MAR-2021","1-FEB-2021")	Microsoft's own documented example, using text dates parsed as if by DATEVALUE	42	42 Provenance Exact example from the DAYS function documentation	Matched
=DAYS(DATE(2021,12,31),DATE(2021,1,1))	A second literal example from the same Microsoft documentation page	364	364 Provenance Dec 31, 2021 minus Jan 1, 2021 = 364 days	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
=DAYS(DATE(2024,3,15),DATE(2024,3,1))	DAYS takes END_DATE FIRST, then start_date -- the opposite argument order from DAYS360/YEARFRAC. Verified via https://support.microsoft.com/en-us/office/days-function-57740535-d549-4395-8728-0f07bff0b9df ("DAYS(end_date, start_date)")	14	14 Provenance 2024-03-15 minus 2024-03-01 = 14 days	Matched
=DAYS(DATE(2024,3,1),DATE(2024,3,15))	Swapping which date is passed first (now the earlier date is 'end_date') flips the sign -- reinforcing that argument order is significant and not auto-corrected	-14	-14 Provenance Same two dates as DAYS_basic_end_first_argument_order but with roles swapped -> -14	Matched
=DAYS("15-MAR-2021","1-FEB-2021")	Microsoft's own documented example, using text dates parsed as if by DATEVALUE	42	42 Provenance Exact example from the DAYS function documentation	Matched
=DAYS(DATE(2021,12,31),DATE(2021,1,1))	A second literal example from the same Microsoft documentation page	364	364 Provenance Dec 31, 2021 minus Jan 1, 2021 = 364 days	Matched

LibreOffice Calc 25.8.7.3 (tested 2026-07-29)

Formula	Description	Result	Expected	Verdict
=DAYS(DATE(2024,3,15),DATE(2024,3,1))	DAYS takes END_DATE FIRST, then start_date -- the opposite argument order from DAYS360/YEARFRAC. Verified via https://support.microsoft.com/en-us/office/days-function-57740535-d549-4395-8728-0f07bff0b9df ("DAYS(end_date, start_date)")	14	14 Provenance 2024-03-15 minus 2024-03-01 = 14 days	Matched
=DAYS(DATE(2024,3,1),DATE(2024,3,15))	Swapping which date is passed first (now the earlier date is 'end_date') flips the sign -- reinforcing that argument order is significant and not auto-corrected	-14	-14 Provenance Same two dates as DAYS_basic_end_first_argument_order but with roles swapped -> -14	Matched
=DAYS("15-MAR-2021","1-FEB-2021")	Microsoft's own documented example, using text dates parsed as if by DATEVALUE	42	42 Provenance Exact example from the DAYS function documentation	Matched
=DAYS(DATE(2021,12,31),DATE(2021,1,1))	A second literal example from the same Microsoft documentation page	364	364 Provenance Dec 31, 2021 minus Jan 1, 2021 = 364 days	Matched

Docs & syntax

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

Where DAYS behaves differently

DATEDIF across Excel, Google Sheets and LibreOffice
DATEDIF's "MD" bug is reproduced exactly in LibreOffice, so migrating will not fix it — but end-before-start returns #VALUE! instead of Excel's documented #NUM!.