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UnixToDateTime

function UnixToDateTime(U: Int64): TDateTime;

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := UnixToDateTime(86400); // 2 January 1970 at 00:00
end;

Usage​

UnixToDateTime converts signed Unix seconds using Velox's direct epoch arithmetic and returns an untagged TDateTime.

Parameters

NameTypeDescription
UInt64Signed seconds relative to the Unix epoch.

Returns

The raw result of U / 86400 + 25569, where 25569 is Velox's day number for the Unix epoch.

Behaviour

  • 0 returns the Unix epoch midnight and 86400 returns the following midnight.
  • Non-multiples of 86,400 produce a fractional day and retain sub-day seconds subject to Double precision.
  • Negative values before 1970 are accepted as arithmetic input.

Errors

No function validation or exception handling. The arithmetic usually returns a numeric value even when it is not a usable encoded date.

Additional Technical Info​

UnixToDateTime converts a signed count of seconds from 1970-01-01 00:00:00 using Velox's own arithmetic. The result is untagged and no local/UTC conversion is performed; conventional use therefore treats the returned fields as UTC by agreement.

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

Implementation

The modified PascalScript runtime registers a Velox/PascalScript-owned helper. It does not call installed Delphi 37.0 System.DateUtils.UnixToDateTime. The custom terminal performs one floating division and one addition, with no timezone option, timestamp helper or calendar validation.

Edge cases and quirks

  • Delphi's same-name routine has an AReturnUTC option and uses DateUtils increment/timezone logic; those are not part of the Velox entry.
  • No range check ensures that the result is a valid Delphi calendar date. Extreme Int64 input can return a raw Double far outside years 1..9999; later date routines can then fail.
  • For Unix instants before Delphi's 30 December 1899 epoch, direct mathematical negative fractions do not follow Delphi's special negative TDateTime time encoding. Timed pre-epoch values can therefore decode to the wrong clock fields. Date-only negative integers avoid that fractional defect.
  • Large magnitudes lose single-second precision when converted through Double.
  • The returned number has no UTC marker. Passing it to UTCtoLocal applies that helper's separate legacy current-offset rule.

Side effects

None; the helper does not read the host clock or timezone.

Performance and concurrency

Constant-time numeric arithmetic with no allocation or shared state.

Related entries

  • DateTimeToUnix is Velox's rounded arithmetic conversion in the other direction.
  • UTCtoLocal applies the host's sampled current offset.
  • IncSecond performs timestamp-normalised second increments.

External references

These pages document same-purpose upstream routines for comparison; neither is the terminal used by Velox:

Created 2026-07-15