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DateOf

Function DateOf(const AValue: TDateTime): TDateTime

Example​

procedure ScriptEvent(var Value: variant);
var
  Timestamp: TDateTime;
begin
  Timestamp := EncodeDate(2026, 7, 18) + EncodeTime(14, 30, 0, 0);
  Value := DateOf(Timestamp); // 18 July 2026 at midnight
end;

Usage​

DateOf removes the time component by truncating a TDateTime value to its date portion.

Parameters

NameTypeDescription
AValueTDateTime, constDate/time value from which to remove the time component.

Returns

Trunc(AValue), normally representing the same calendar date at midnight.

Behaviour

For an ordinary encoded value, every timestamp on the same day produces the same result. The routine neither rounds nor validates the floating value and does not convert between local time and UTC.

Errors

Valid finite values do not raise. The function does not validate NaN, infinity or an out-of-domain numeric date.

Usage notes

Use DateOf when you already have a timestamp. Use Date only when you specifically need the host's current local date.

Additional Technical Info​

DateOf removes the time of day from an existing TDateTime value without reading a clock or applying timezone rules. It returns the value's integral Delphi date component.

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

Implementation

The DateUtils import binds directly to Delphi 37.0 System.DateUtils.DateOf. Its entire terminal implementation is Result := Trunc(AValue).

Edge cases and quirks

  • For pre-epoch values, Delphi encodes the time as the magnitude of a negative fraction. Trunc still removes that time according to Delphi's convention; do not replace it with Floor, which would select a different integer for negative values.
  • Floating-point arithmetic can produce a value just across an intended midnight boundary. Because DateOf simply truncates, it can then return the adjacent date. Embarcadero recommends rounding an imprecisely calculated value before applying DateOf when this risk exists.
  • A result of 0.0 is the valid Delphi epoch date, 30 December 1899, not an error sentinel.
  • Free Pascal implements the same Trunc operation, but its reference is compatibility information rather than the runtime used by Velox.

Side effects

None.

Performance and concurrency

Constant-time scalar truncation with no allocation or shared state.

Related entries

  • Date obtains the current local date.
  • DecodeDate returns year, month and day as separate values.
  • CompareDate compares two date portions without returning them.

External references

Created 2026-07-15