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vxTryStrToDate

function vxTryStrToDate(
  const S: string;
  out Value: TDateTime): Boolean;

Example​

procedure ScriptEvent(var Value: variant);
var
  ParsedDate: TDateTime;
begin
  // For a host whose system short-date order is day/month/year:
  if vxTryStrToDate('31/12/2026', ParsedDate) then
    Value := ParsedDate
  else
    Value := Null;
end;

Usage​

vxTryStrToDate attempts a system-locale date conversion and reports whether the output value is valid.

Parameters

NameTypeDescription
Sstring, constDate text in the Windows system short-date grammar.
ValueTDateTime, outReceives a valid date at midnight when the function returns True. Do not use it when the function returns False.

Returns

True only when the locale scanner consumes the whole source and encodes a valid date; otherwise False.

Behaviour

The Boolean is the authoritative validity result. Successful two-field dates can receive the current year; two-digit years are expanded through the captured TwoDigitYearCenturyWindow. A successful Value has no time or timezone component.

Errors

Ordinary date conversion failures return False. Locale acquisition, allocation and unexpected runtime exceptions are not caught by the function.

Additional Technical Info​

vxTryStrToDate attempts to parse a complete Windows system-locale date. It returns True and writes the midnight date on success, or returns False for ordinary syntax/range failure without raising EConvertError.

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

Implementation

The scripting import binds to vxFormats.vxTryStrToDate. The wrapper constructs TFormatSettings.Create(LOCALE_SYSTEM_DEFAULT) and calls System.SysUtils.TryStrToDate(S, Value, AFormatSettings). The installed Delphi terminal derives a token sequence from ShortDateFormat, scans locale fields/names, applies current-year and short-year rules, calls TryEncodeDate, and requires its position to pass the end of the input.

Edge cases and quirks

  • A valid date can yield Value=0.0 for 30 December 1899 while the function returns True; always test the Boolean rather than the numeric value.
  • The system date order/separator can differ from both a user's workstation and a remote file's declared format.
  • Wrong separators, impossible leap dates, time suffixes and extra trailing characters return False.
  • Omitted-year and short-year results depend on the current year and system century-window setting.
  • Locale name forms are accepted only when requested by ShortDateFormat; weekday names, when scanned, are checked against the final date.
  • Value is not a business fallback on False. Treat it as unusable even if a build appears to preserve or partially assign it.
  • Free Pascal's linked routine documents broader one-number input and explicitly identifies it as non-Delphi behaviour. It does not expand Velox's accepted forms.

Side effects

The caller's output variable is written on success. No persistent Velox data is changed.

Performance and concurrency

The scan is linear with bounded locale-name comparison. Explicit local settings avoid Delphi global-format races; later system-locale or year changes can affect subsequent calls.

Remarks

This is the preferred locale-date entry when invalid optional input is expected and must be handled explicitly. It is not a parser for a remote partner's fixed date format unless that format is guaranteed to match the Velox host system locale.

Related entries

External references

Created 2026-07-15