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WithinPastYears

Function WithinPastYears( const ANow, AThen : TDateTime; const AYears : Integer) : Boolean

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := WithinPastYears(
    EncodeDate(2021, 1, 1), EncodeDate(2022, 1, 1), 0);
  // Value is True: 365 days contains 0 complete 365.25-day periods.
end;

Usage​

WithinPastYears reports whether two date/time values are within a supplied count of complete approximate 365.25-day years.

Parameters

NameTypeDescription
ANowTDateTimeOne encoded date/time endpoint. It need not be the later or actual current value.
AThenTDateTimeThe other encoded endpoint.
AYearsIntegerInclusive maximum count of complete 365.25-day periods. Negative values produce False.

Returns

True when YearsBetween(ANow, AThen) <= AYears; otherwise False.

Behaviour

The result is symmetric. A 365-day common-year interval contains 0 complete approximate years and therefore passes a limit of 0; a 366-day leap-year interval contains 1. This is duration arithmetic, not an age or anniversary calculation.

Errors

Velox does not catch conversion or arithmetic errors produced by invalid/non-representable values.

Additional Technical Info​

Reports whether two encoded date/time values are no more than AYears complete approximate years apart. An approximate year is fixed at 365.25 days; calendar anniversaries, leap-day adjustment and matching month/day fields are not used.

Implementation

Velox binds directly to System.DateUtils.WithinPastYears. YearsBetween converts both values to millisecond timestamps, takes the absolute difference and divides it by Round(86,400,000 * 365.25), or 31,557,600,000 milliseconds. Integer division floors that count before the inclusive comparison.

Edge cases and quirks

  • The permissive floor is intentional in the installed function: 2.9 approximate years passes a limit of 2.
  • Use IncYear and explicit date comparison when calendar-anniversary semantics are required.
  • Negative limits return False, even for equal inputs.
  • Inputs are millisecond-normalised, but no timezone/daylight-saving rules are applied.
  • Free Pascal documents the same approximate family. Velox exposes only Delphi's three-argument predicate and follows the installed 365.25-day constant.

Performance and concurrency

The operation is constant-time integer arithmetic, allocation-free and independent of shared Velox state.

Related entries

  • YearsBetween — returns the complete approximate-year count used here.
  • YearSpan — returns a fractional approximate-year span through raw arithmetic.
  • IncYear — shifts a date by calendar years with different leap-day behaviour.

External references

Created 2026-07-15