ISLEAPYEAR Function (OpenOffice Calc)

• Introduced: First release not established; documented by OpenOffice.org 3.3.
• Supported in: Apache OpenOffice 4.1.16; this is a verified release, not a final supported version.
• Scope: Desktop Calc, English function names and semicolon-separated formulas.
• Checked: October 14, 2026. Eight ordinary reference formulas were recalculated from generated ODF in 4.1.16 on Linux x86-64, Build 9816. Source and independent calendar arithmetic were checked.

ISLEAPYEAR returns numeric 1 when the year containing Date is a Gregorian leap year, otherwise numeric 0. The date add-in tests the extracted calendar year; it does not interpret a bare integer as a year label. Release implementation.

ISLEAPYEAR(Date)

• Date: a required date serial or date cell. For a year held as a number in A2, use ISLEAPYEAR(DATE(A2;1;1)).
• The implementation takes an integer serial and returns an integer indicator. Cell formatting may present logical-looking output, but the retained examples contain numeric 1 or 0.

The native column contains saved 4.1.16 results; independent references use exact date arithmetic or rational fractions. Numerical values are shown to twelve decimal places where needed. Enter the DATE expressions directly rather than substituting locale-dependent text.

The generated ODF uses ORG.OPENOFFICE.ISLEAPYEAR, mapped to the English worksheet name ISLEAPYEAR by the release function map. The saved operation was verified after recalculation. This establishes the ODF-format path rather than manual English-name entry.

=ISLEAPYEAR(DATE(2024;2;15)) gives 1, and the 2023 equivalent gives 0. If A2 stores the year 2024 as a number, =ISLEAPYEAR(DATE(A2;1;1)) is the appropriate construction. Passing A2 directly would ask about serial 2024.

For a date in B2, a readable label can be built with =IF(ISLEAPYEAR(B2);"Leap year";"Common year"). This uses the indicator without assuming every year divisible by four is a leap year.

A Gregorian year is leap when it is divisible by 4 and either not divisible by 100 or also divisible by 400. The independent rule is MOD(y;4)=0 together with the century exception. Years 1900 and 2100 fail it; 2000 passes. Those century cases are included in the native examples.

For valid date inputs, 365+ISLEAPYEAR(B2) gives the containing year’s calendar-day count. February has 28+ISLEAPYEAR(B2) days when B2 lies in that February. A leap year does not add a day to every month, and it does not by itself identify the week-numbering year at January boundaries.

Use four-digit years through DATE when you start from a year value. The function follows the Gregorian rule used by the implementation; it is not a test of whether a historical jurisdiction had adopted that calendar.

The eight examples use valid date-only values. Text parsing, missing dates, fractional serial conversion and arbitrary extreme years were not executed. The generated ODF uses the release-registered ORG.OPENOFFICE storage identity; it is not proof of manual formula entry in every locale.

DATE, DAYSINYEAR, DAYSINMONTH.

• Function-specific release implementation

The generated ODF produced the informational load warning “Not all attributes could be read.” The sheet was hard-recalculated and saved separately. All eight ordinary function identities and results were reconciled; a stale SUM cache changed from 999999 to 3 and an uncached SUM returned 7. This establishes the stated examples, not every workbook style or invalid input. Other explanatory identities are independent calculations. The authoring-tool XLSX was not executed in OpenOffice, and its preview values are not the native results reported here.