EOMONTH 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.

EOMONTH returns the last calendar day of the month that lies Months away from StartDate’s month. Months=0 returns the current month’s final day. Unlike EDATE, the starting day number does not need to be preserved. Release implementation.

EOMONTH(StartDate;Months)

• StartDate: required date value, date cell or DATE expression.
• Months: required signed integer offset. Zero selects the input month; positive and negative values select later and earlier months.
• These examples use whole dates and offsets. Both implementation parameters are integer-valued.

The native serials are also interpreted as Gregorian calendar dates under the workbook’s 1899-12-30 date epoch. Numerical values are shown to twelve decimal places where needed. Enter the DATE expressions directly rather than substituting locale-dependent text.

=EOMONTH(DATE(2024;1;15);0) gives January 31, 2024. With offset 1 it gives February 29. =EOMONTH(DATE(2024;3;15);-1) also gives February 29. The input need not already be a month-end date.

For a reporting-month start, use =EOMONTH(A2;-1)+1. With A2=March 15, 2024, the previous month-end is February 29 and the next day is March 1. An exclusive next-month boundary is =EOMONTH(A2;0)+1; this is often clearer than adding a nearly-one-day timestamp to the final date.

The source moves the calendar month and asks for its length before returning that month’s last date. December rollover is included in the examples: December 31, 2024 plus 12 months gives December 31, 2025. The independent month-index calculation agrees with all eight serial results.

For whole offsets in the ordinary supported range, repeated EOMONTH steps remain at month-end. Starting January 31, 2024 and stepping one month twice yields February 29 and March 31. EDATE instead retains the clamped day in a chained schedule, so its second step would be March 29. Choose the function from the scheduling rule.

Format the numeric answer as a date when that is the intended presentation. The table’s calendar interpretation uses the tested workbook’s 1899-12-30 date epoch; copying bare serials into another date system requires care.

The tests cover ordinary dates and whole offsets. Fractional month conversion, invalid dates and extreme date limits were not executed. A month-end reporting boundary is not by itself a business-day adjustment; weekends and holidays require a separate rule.

DATE, EDATE, DAYSINMONTH.

• Function-specific release implementation
• DaysInMonth helper
• DateToDays helper

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.