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IsValidDate

Function IsValidDate(const AYear, AMonth, ADay: Word): Boolean

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := IsValidDate(2024, 2, 29); // True
end;

Usage​

IsValidDate validates Gregorian year, month and day fields against Velox's supported calendar range.

Parameters

NameTypeDescription
AYearWord, constGregorian year; valid range 1 through 9999.
AMonthWord, constMonth; valid range 1 through 12.
ADayWord, constDay of month; upper bound depends on year and month.

Returns

True only when all three fields describe a supported Gregorian date.

Behaviour

  • Leap-year rules are applied when February's length is calculated.
  • Zero is invalid for every field.
  • The routine validates only; it does not normalise values such as month 13 or day 32.

Important usage notes

  • Arguments are Word, so negative inputs cannot be represented by the declared interface.
  • A year beyond 9999 returns False even though it fits in Word.
  • Use the matching encoder only after a True result; validation does not create a TDateTime.

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​

IsValidDate validates Gregorian year, month and day fields against Delphi's supported calendar range.

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.IsValidDate. It checks year 1–9999 and month 1–12, then compares the day with DaysInAMonth(AYear, AMonth). Short-circuit evaluation avoids the month-length call when the year or month is already out of range.

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