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vxMilliSecsSpan

Function vxMilliSecsSpan(const ANow, AThen: TDateTime): Int64

Example​

procedure ScriptEvent(var Value: variant);
var
  FirstTime, SecondTime: TDateTime;
begin
  FirstTime := EncodeTime(9, 0, 0, 0);
  SecondTime := EncodeTime(9, 0, 1, 250);
  Value := vxMilliSecsSpan(FirstTime, SecondTime); // 1250
end;

Usage​

vxMilliSecsSpan returns the signed millisecond-of-day difference from the first encoded time to the second, ignoring both dates.

Parameters

NameTypeDescription
ANowTDateTime, constFirst value; only its decoded time-of-day is used.
AThenTDateTime, constSecond value; only its decoded time-of-day is used.

Returns

millisecondsOfDay(AThen) - millisecondsOfDay(ANow) as an Int64. The practical result range for valid times is -86,399,999..86,399,999.

Behaviour

  • Argument order matters; reversing the inputs negates the result.
  • Dates are ignored even when the values are on different calendar days.
  • Resolution is one decoded millisecond.

Errors

No Velox exception handling surrounds decoding. Invalid or non-finite TDateTime input can fail in the RTL.

Additional Technical Info​

vxMilliSecsSpan subtracts the first input's millisecond-of-day index from the second input's index. It is signed and deliberately ignores the calendar date portion of both values.

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

Implementation

The Velox date-tools import binds to vxDateTools.vxMilliSecsSpan. It calls System.SysUtils.DecodeTime for each input, calculates hour*3,600,000 + minute*60,000 + second*1,000 + millisecond, and subtracts the two Int64 totals.

Edge cases and quirks

  • This is not equivalent to MilliSecondsBetween. The latter is absolute, date-aware and timestamp-normalised.
  • A normal midnight crossing is not inferred. From 23:59 to 00:01 the function returns a large negative value, not positive two minutes.
  • ANow and AThen are conventional names only; no clock is read and no ordering is enforced.
  • DecodeTime normalises valid pre-epoch representations before extracting fields, but the date is then discarded.
  • Inputs with different timezone conventions are compared only as displayed clock fields.

Side effects

None.

Performance and concurrency

Constant-time decoding and integer arithmetic with no allocation or shared state.

Related entries

External references

The Velox algorithm is custom; these pages document the terminal time decoder used by it:

Created 2026-07-15