TryEncodeDateDay

Function TryEncodeDateDay(const AYear, ADayOfYear: Word;
  var AValue: TDateTime): Boolean

Example

procedure ScriptEvent(var Value: variant);
var
  EncodedDate: TDateTime;
begin
  if TryEncodeDateDay(2028, 60, EncodedDate) then
    Value := EncodedDate; // 29 February 2028
end;

Usage

TryEncodeDateDay tries to construct midnight from a Gregorian year and one-based day-of-year ordinal.

Parameters

Name	Type	Description
AYear	Word, const	Gregorian year 1..9999.
ADayOfYear	Word, const	Ordinal 1..365, or 1..366 in a leap year.
AValue	TDateTime, var	Receives the requested date at midnight only on success.

Returns

True for a valid year-local ordinal; otherwise False.

Important usage notes

• Day 60 is 29 February in a leap year and 1 March in a common year.
• Zero is invalid and does not mean the preceding year's final day.
• Day 366 returns False for a common year rather than rolling into the next year.
• AValue is not assigned when validation fails. The script declaration is var, so do not consume its prior value unless the result is True.
• The resulting midnight has no timezone tag.

Errors

Normal year/ordinal validation failures return False. No Velox function translates unexpected runtime faults.

Additional Technical Info

TryEncodeDateDay converts a Gregorian year and one-based ordinal day into a date at midnight. Invalid year/ordinal combinations return False rather than raising the corresponding DateUtils conversion error.

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.TryEncodeDateDay. It calls IsValidDateDay; when valid it constructs 1 January with StartOfAYear and adds ADayOfYear - 1 whole days.

Side effects

Writes AValue on success only. No other state changes.

Performance and concurrency

Constant bounded calendar validation and arithmetic with no shared state.

Related entries

• EncodeDateDay raises instead of returning a success flag.
• DecodeDateDay performs the inverse decomposition.
• DayOfTheYear extracts the one-based ordinal.

External references

• Embarcadero System.DateUtils.TryEncodeDateDay
• Free Pascal TryEncodeDateDay

Created 2026-07-15