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IsValidDateMonthWeek

Function IsValidDateMonthWeek(const AYear, AMonth, AWeekOfMonth, ADayOfWeek: Word): Boolean

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := IsValidDateMonthWeek(2026, 2, 5, 1); // True, although February 2026 has no fifth Monday
end;

Usage​

IsValidDateMonthWeek validates the field ranges of an ISO month-week date without constructing the resulting date.

Parameters

NameTypeDescription
AYearWord, constYear; valid range 1 through 9999.
AMonthWord, constMonth; valid range 1 through 12.
AWeekOfMonthWord, constWeek occurrence; accepted range 1 through 5.
ADayOfWeekWord, constMonday-based weekday; 1 is Monday and 7 is Sunday.

Returns

True when every field lies inside its broad numeric range; otherwise False.

Behaviour

  • The weekday numbering is Monday 1 through Sunday 7.
  • Week five is accepted for every month and weekday combination.
  • Zero is invalid for every field.

Important usage notes

  • A True result does not prove that the requested fifth weekday actually occurs in the specified month, or that a later conversion will produce an owned date under the caller's intended convention. The example deliberately demonstrates this gap.
  • The function checks fields, not an ISO-8601 week-of-year value; use IsValidDateWeek for that representation.
  • Arguments are Word, so negative input cannot be represented.

Usage notes

Use the result as the documented field or date predicate only. It does not establish a timezone, business calendar or input provenance.

Additional Technical Info​

IsValidDateMonthWeek validates the field ranges of an ISO month-week date without constructing the resulting date.

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

Implementation

The DateUtils import binds directly to Delphi 37.0 System.DateUtils.IsValidDateMonthWeek. It consists only of direct range checks: year 1–9999, month 1–12, week 1–5 and weekday 1–7. It does not encode a date or inspect a calendar.

Side effects

None.

Errors

There is no wrapper exception handling. Ordinary out-of-range Word fields return False rather than raising.

Performance and concurrency

Constant-time field decoding or comparison with no external I/O. The routine uses no shared mutable state.

Related entries

External references

Created 2026-07-15