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SecondOfTheDay

Function SecondOfTheDay( const AValue : TDateTime) : LongWord

Example​

procedure ScriptEvent(var Value: variant);
var
  InputValue: TDateTime;
begin
  InputValue := EncodeDateTime(2026, 7, 16, 13, 5, 7, 900);
  Value := SecondOfTheDay(InputValue); // 47107
end;

Usage​

SecondOfTheDay returns the zero-based second index within the encoded day.

Parameters

NameTypeDescription
AValueTDateTime, constValue whose hour, minute and second fields are indexed.

Returns

A LongWord from 0 at midnight through 86,399 at 23:59:59.

Behaviour

  • The index resets to zero at each encoded midnight.
  • Milliseconds are discarded, not rounded.
  • The calendar date does not affect the result.
  • The value represents encoded clock fields, not timezone-aware elapsed seconds through a daylight-saving day.

Errors

Decode exceptions propagate unchanged.

Usage notes

Use SecondsBetween for an interval between two complete date/time values.

Additional Technical Info​

SecondOfTheDay returns the zero-based whole-second position of the encoded clock time within its day.

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

Implementation

The DateUtils import binds to System.DateUtils.SecondOfTheDay. Delphi decodes hour, minute, second and millisecond, then calculates second + (minute + hour * 60) * 60. The millisecond field is intentionally unused.

Edge cases and quirks

  • Every encoded day is treated as exactly 86,400 field seconds even when a real local day has a daylight-saving transition.
  • Invalid raw input can fail while decoding.
  • The exposed LongWord corresponds to Delphi's unsigned Cardinal.
  • Free Pascal's same-name page describes the compatible zero-based day index.

Side effects

None.

Performance and concurrency

Constant-time decoding and arithmetic with no external state.

Related entries

External references

Created 2026-07-15