DAY

Quirk found

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

Real compatibility results for the DAY 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)	Quirk found
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 DAY’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 DAY working in LibreOffice?

DAY 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.

Why isn’t DAY working in Google Sheets?

DAY runs in Google Sheets, but our executed cases show it does not match Excel’s documented behavior on every input (the failing cases are listed on this page). If a formula that behaves one way in Excel gives you a different answer in Sheets, compare your usage against those cases before assuming your data is wrong.

Discovered quirks

=DAY(1) on Google Sheets returned 31, but the documented/expected result is 1.
Provenance
Serial 1 is Jan 1, 1900 in the 1900 date system; MISMATCH vs expected: expected 1, got 31
=DAY(1) on LibreOffice Calc returned 31, but the documented/expected result is 1.
Provenance
Serial 1 is Jan 1, 1900 in the 1900 date system; MISMATCH vs expected: expected 1, got 31

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
=DAY(DATE(2024,3,15))	DAY applied to a constructed date	15	15	Matched
=DAY(1)	DAY applied directly to the raw serial number 1 (Jan 1, 1900)	1	1 Provenance Serial 1 is Jan 1, 1900 in the 1900 date system	Matched
=DAY(45366.75)	A serial with a fractional (time-of-day) component still resolves to the correct calendar day	15	15 Provenance 45366 = 2024-03-15; the .75 fractional day is ignored by DAY	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
=DAY(DATE(2024,3,15))	DAY applied to a constructed date	15	15	Matched
=DAY(1)	DAY applied directly to the raw serial number 1 (Jan 1, 1900)	31	1 Provenance Serial 1 is Jan 1, 1900 in the 1900 date system	Mismatch
=DAY(45366.75)	A serial with a fractional (time-of-day) component still resolves to the correct calendar day	15	15 Provenance 45366 = 2024-03-15; the .75 fractional day is ignored by DAY	Matched

LibreOffice Calc 25.8.7.3 (tested 2026-07-29)

Formula	Description	Result	Expected	Verdict
=DAY(DATE(2024,3,15))	DAY applied to a constructed date	15	15	Matched
=DAY(1)	DAY applied directly to the raw serial number 1 (Jan 1, 1900)	31	1 Provenance Serial 1 is Jan 1, 1900 in the 1900 date system	Mismatch
=DAY(45366.75)	A serial with a fractional (time-of-day) component still resolves to the correct calendar day	15	15 Provenance 45366 = 2024-03-15; the .75 fractional day is ignored by DAY	Matched

Docs & syntax

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

Related how-to recipes

Where DAY behaves differently

DAY(1), MONTH(1) and YEAR(1): Excel disagrees with Sheets and LibreOffice
Serial number 1 is Jan 1 1900 in Excel but Dec 31 1899 in both Google Sheets and LibreOffice (executed), so DAY/MONTH/YEAR of a raw serial silently disagree. Why, and how to migrate.