okay:

while ($__month >= 0){
       $days = $days + $monthdays[$__month];
       --$__month;
   }
[download]

for "2/1" $__month is 2, you'll add 28 + 31 + 1 and get '60'.
So my fix didn't work so well. Either knock one off the month to start w/ or put "0" at the beginning of the month array so that $__month == 0 adds zero, not 31. i.e.

@monthdays = ("0", "31","28","31","30","31","30","31","31","30","31","
+30","31");
my $days = 0;

while (--$__month >= $[){
    $days = $days + $monthdays[$__month];
    #--$__month;
}
$days = $days + $__day;
[download]

while (--$__month >= 0 )

a