This is by design and is documented in the readme file: "AgeCalculator treats 'one month' as the interval from a given day in one month to the same day, or as close to it as possible, in the following month." The example given is "31-Jan-2004 to 29-Feb-2004 is 1 month (last day to last day)".
>
> .CalculateAge({^1988/10/31} , {^1998/11/30 })
> ? .nYears, .nMonths , .nDays
>Observed 10,1,0
>Expected 10,0,30
>
Rick Borup, MCSD
recursion (rE-kur'-shun) n.
see recursion.