Skip to main content

WithinPastMilliSeconds

Function WithinPastMilliSeconds( const ANow, AThen : TDateTime; const AMilliSeconds : Int64) : Boolean

Example​

procedure ScriptEvent(var Value: variant);
var
  FirstValue, SecondValue: TDateTime;
begin
  FirstValue := EncodeDateTime(2026, 4, 1, 9, 0, 0, 0);
  SecondValue := EncodeDateTime(2026, 4, 1, 9, 0, 1, 500);
  Value := WithinPastMilliSeconds(FirstValue, SecondValue, 1500);
  // Value is True because the encoded distance is exactly 1,500 ms.
end;

Usage​

WithinPastMilliSeconds reports whether two date/time values are within an inclusive millisecond-distance limit.

Parameters

NameTypeDescription
ANowTDateTimeOne encoded date/time endpoint; it need not be the later endpoint.
AThenTDateTimeThe other encoded date/time endpoint.
AMilliSecondsInt64Inclusive distance limit in milliseconds. Negative values produce False.

Returns

True when MilliSecondsBetween(ANow, AThen) <= AMilliSeconds; otherwise False.

Behaviour

DateTimeToTimeStamp rounds each binary floating-point input to the nearest encoded millisecond. There is no sub-millisecond result: two values that normalise to the same millisecond have distance 0.

Errors

Velox adds no validation or exception handler. Invalid, non-finite or non-representable inputs can propagate RTL arithmetic/conversion failures.

Additional Technical Info​

Reports whether the absolute millisecond-normalised distance between two encoded date/time values is less than or equal to AMilliSeconds. It is the finest-grained member of the WithinPast* family exposed by Velox.

Implementation

Velox binds directly to System.DateUtils.WithinPastMilliSeconds. MilliSecondsBetween converts each TDateTime to a TTimeStamp, combines its date and time into an Int64 millisecond count, subtracts the values and takes the absolute result. The predicate compares that value directly with the supplied limit.

Edge cases and quirks

  • The test is symmetric and does not establish which value is earlier.
  • AMilliSeconds = 0 tests millisecond-normalised equality, not bit-for-bit equality of the original Double values.
  • Negative limits return False, even when the normalised endpoints are equal.
  • No timezone or daylight-saving conversion occurs; the inputs are untagged encoded timestamps.
  • Free Pascal describes fractional milliseconds as discarded. In installed Delphi 37.0 the explicit terminal operation is nearest-millisecond timestamp rounding.

Performance and concurrency

The operation is constant-time and allocation-free, with no clock or shared-state access.

Related entries

External references

Created 2026-07-15