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EndOfAMonth

Function EndOfAMonth(const AYear, AMonth: Word): TDateTime

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := EndOfAMonth(2028, 2); // 2028-02-29 23:59:59.999
end;

Usage​

EndOfAMonth returns the final millisecond of the last calendar day in a supplied valid year and month.

Parameters

NameTypeDescription
AYearWord, constGregorian year 1..9999.
AMonthWord, constCalendar month 1..12.

Returns

The month-ending date at 23:59:59.999.

Errors

Invalid input propagates the RTL failure. For an invalid month, do not depend on a particular exception class because the table lookup precedes normal date validation.

Additional Technical Info​

EndOfAMonth returns the last millisecond of the named calendar month, accounting for month length and leap years.

The example is fictional, deterministic and source-reviewed. It was not executed by the documentation workflow.

Implementation

The DateUtils import binds directly to Delphi 37.0 System.DateUtils.EndOfAMonth. The terminal obtains the month length from the MonthDays table through DaysInAMonth, encodes that final calendar date, then recodes its time to the day's final millisecond.

Edge cases and quirks

  • February returns day 28 or 29 according to IsLeapYear(AYear).
  • The installed implementation indexes its month-length table before EncodeDate validates the fields. An out-of-range AMonth is therefore an unsafe input and can produce a range/index failure rather than the tidy EConvertError a caller might expect from a date encoder. Validate 1..12 before calling.
  • The last-millisecond boundary has the same higher-precision filtering caveat as EndOfADay.
  • No timezone or daylight-saving transition is applied.

Side effects

None.

Performance and concurrency

Constant-time table lookup and calendar arithmetic. The month table is read-only.

Related entries

  • EndOfTheMonth derives the year and month from an existing value.
  • EndOfAYear returns the equivalent year boundary.

External references

Created 2026-07-15