Skip to main content

MilliSecondOfTheMonth

Function MilliSecondOfTheMonth(const AValue: TDateTime): LongWord

Example​

procedure ScriptEvent(var Value: variant);
var
  InputValue: TDateTime;
begin
  InputValue := EncodeDateTime(2026, 7, 2, 1, 2, 3, 4);
  Value := MilliSecondOfTheMonth(InputValue); // 90123004
end;

Usage​

MilliSecondOfTheMonth returns the zero-based millisecond index within the encoded calendar month.

Parameters

NameTypeDescription
AValueTDateTime, constEncoded date/time whose position within its calendar month is required.

Returns

A LongWord from zero through one less than the number of milliseconds in the encoded month. The maximum is 2,419,199,999 for a 28-day month, 2,505,599,999 for 29 days, 2,591,999,999 for 30 days or 2,678,399,999 for 31 days.

Behaviour

  • Midnight on the first day of a month returns zero.
  • The result increases through the encoded month and resets at midnight on the first day of the next month.
  • Leap-year rules affect the February maximum.
  • Smaller-than-millisecond fractions are resolved by Velox's date/time decoding before the result is calculated.
  • No timezone or daylight-saving conversion is performed.

Errors

Velox performs no validation or exception translation. Date/time decode exceptions propagate to the script.

Usage notes

Use this function for an index or bucket within the encoded month. Use MilliSecondsBetween when the requirement is a duration between two values.

Additional Technical Info​

MilliSecondOfTheMonth returns the zero-based position of an encoded date/time within its calendar month, measured in whole milliseconds from midnight on the first day. It is a calendar-field index, not a duration calculation between two independent values.

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.MilliSecondOfTheMonth. The routine obtains the zero-based whole-second index within the month, multiplies it by 1,000 and adds the decoded millisecond-within-second component.

Edge cases and quirks

  • The result describes encoded calendar fields. It is not the number of real elapsed milliseconds since a timezone-aware month boundary.
  • Although the exposed return type is LongWord, the installed Delphi terminal declares the equivalent 32-bit unsigned type Cardinal.
  • The maximum for a 31-day month fits within an unsigned 32-bit result but not within a signed 32-bit integer. Preserve the unsigned value or use a wider numeric destination when subsequent arithmetic is required.
  • Invalid or non-finite encoded input can raise during component decoding rather than returning a sentinel.

Side effects

None.

Performance and concurrency

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

Related entries

External references

Created 2026-07-15