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IsValidTime

Function IsValidTime(const AHour, AMinute, ASecond, AMilliSecond: Word): Boolean

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := IsValidTime(24, 0, 0, 0); // True
end;

Usage​

IsValidTime validates hour, minute, second and millisecond fields, including DateUtils' exact 24:00 special case.

Parameters

NameTypeDescription
AHourWord, constHour to validate.
AMinuteWord, constMinute to validate.
ASecondWord, constSecond to validate.
AMilliSecondWord, constMillisecond to validate.

Returns

True for 00:00:00.000 through 23:59:59.999, and also for exactly 24:00:00.000.

Behaviour

  • Midnight can be expressed as ordinary 00:00:00.000.
  • Exactly 24:00:00.000 is additionally valid as an end-of-day notation.
  • 24:00:00.001, 24:00:01.000 and every hour above 24 are invalid.

Important usage notes

  • EncodeTime and EncodeDateTime do not accept hour 24. Normalise the special end-of-day tuple to midnight on the following date before passing it to those encoders.
  • Second 60 is rejected; there is no leap-second special case.
  • This is field validation only and has no timezone or daylight-saving interpretation.

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​

IsValidTime validates hour, minute, second and millisecond fields, including DateUtils' exact 24:00 special case.

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.IsValidTime. It accepts the ordinary ranges hour 0–23, minute 0–59, second 0–59 and millisecond 0–999. A second branch accepts hour 24 only when every smaller field is zero.

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

  • IsValidDateTime combines this result with Gregorian date validation.
  • EncodeTime constructs ordinary time values but does not accept the 24:00 validation special case.

External references

Created 2026-07-15