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DateTimeToUnix

function DateTimeToUnix(D: TDateTime): Int64;

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := DateTimeToUnix(EncodeDate(1970, 1, 2)); // 86400
end;

Usage​

DateTimeToUnix converts a TDateTime value to a rounded signed count of seconds from the Unix epoch using Velox's timezone-neutral arithmetic.

Parameters

NameTypeDescription
DTDateTimeDate/time value to treat as a timezone-neutral point on the Unix-epoch scale.

Returns

An Int64 calculated as Round((D - 25569) * 86400). Epoch midnight returns 0; earlier values return negative seconds and later values return positive seconds.

Behaviour

The result is a mathematical conversion of the supplied number. To produce a conventional UTC Unix timestamp, D must already represent UTC. Supplying a local wall-clock value simply labels that clock reading as though it were on the same timezone-neutral scale.

Errors

There is no function-level error handling. Numeric conversion exceptions propagate into the script.

Additional Technical Info​

DateTimeToUnix converts the supplied Delphi day count to signed seconds relative to 1970-01-01 00:00:00. The Velox-exposed entry is a custom PascalScript helper. It does not call the similarly named Delphi System.DateUtils function and it does not convert local time to UTC.

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

Implementation

The modified PascalScript compile unit exposes the one-argument signature. Its matching runtime unit registers a Velox/PascalScript-owned helper whose complete formula subtracts the Delphi day number of the Unix epoch (25569), converts days to seconds (86400 per day), then calls Delphi Round.

This differs materially from installed Delphi 37.0 System.DateUtils.DateTimeToUnix(const AValue; AInputIsUTC). The Delphi routine can convert a local value to UTC when asked and uses whole-second SecondsBetween semantics. Velox exposes neither that overload nor its Boolean argument.

Edge cases and quirks

  • Fractions of a second are rounded to the nearest integer, not truncated. Delphi Round uses ties-to-even (banker's rounding), so exact half-second values can round up or down according to the neighbouring even integer.
  • The custom implementation has no daylight-saving ambiguity handling and no AInputIsUTC option. Convert local values explicitly before calling it.
  • Dates before 1970 produce negative values. Rounding around the epoch is symmetric according to Round, not floor-towards-negative-infinity.
  • Timed values before 30 December 1899 expose a further Velox-specific defect. Delphi stores a pre-epoch time as the magnitude of a negative fraction, but this helper subtracts the raw Double directly. For example, a pre-epoch 06:00 value is treated as another quarter-day into the past rather than a quarter-day after that date's midnight. The result is therefore not a correct chronological Unix timestamp for such timed values. Date-only midnights are not affected by this fractional-time defect.
  • Floating-point representation can move a nominal half-second slightly away from the tie. Do not depend on a decimal half being represented exactly after previous arithmetic.
  • Extremely large or non-finite values can exceed Int64/Round range and propagate a numeric exception.
  • The linked official pages document upstream routines with an optional timezone flag. They are comparison references, not the terminal implementation used by this Velox entry.

Side effects

None. In particular, the function does not read the host timezone or clock.

Performance and concurrency

Constant-time floating/integer arithmetic with no allocation or shared state.

Remarks

Record whether a TDateTime variable represents UTC or local time in the surrounding integration design. The type cannot enforce that distinction.

Related entries

External references

Created 2026-07-15