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MilliSecondOfTheYear

Function MilliSecondOfTheYear(const AValue: TDateTime): Int64

Example​

procedure ScriptEvent(var Value: variant);
var
  InputValue: TDateTime;
begin
  InputValue := EncodeDateTime(2026, 1, 2, 0, 0, 0, 250);
  Value := MilliSecondOfTheYear(InputValue); // 86400250
end;

Usage​

MilliSecondOfTheYear returns the zero-based millisecond index within the encoded calendar year.

Parameters

NameTypeDescription
AValueTDateTime, constEncoded date/time whose position within the calendar year is required.

Returns

An Int64 from 0 through 31,535,999,999 in a common year or through 31,622,399,999 in a leap year.

Behaviour

  • 1 January at 00:00:00.000 returns zero.
  • The value resets at the next calendar-year boundary.
  • Gregorian leap-year rules determine whether the range contains 365 or 366 days.
  • Calendar year, not ISO week-year, controls the boundary.

Important usage notes

  • The result requires 64 bits; it does not fit in either a signed or unsigned 32-bit integer at the end of a year.
  • The function returns an encoded calendar-field index, not a timezone-aware elapsed duration since the real-world start of the year.
  • Smaller-than-millisecond fractions are subject to Velox's decode/timestamp rounding.
  • Invalid or non-finite input can raise rather than producing a sentinel.

Errors

Velox does not catch or translate date/time decode exceptions.

Additional Technical Info​

MilliSecondOfTheYear returns the zero-based position of an encoded date/time within its calendar year, measured in whole milliseconds from 1 January at midnight.

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.MilliSecondOfTheYear. The routine calculates the whole-second index within the year, widens it to Int64, multiplies by 1,000 and adds the millisecond-within-second component.

Side effects

None.

Performance and concurrency

Constant-time component extraction and integer arithmetic with no external I/O or shared mutable state.

Remarks

Keep the result in an Int64-capable destination when using it for ordering or arithmetic.

Related entries

External references

Created 2026-07-15