Your solution doesn't always give the right answer.

Then        Now                  Date::Calc   BaldPenguin
----------  -------------------  -----------  -----------
2005/08/01  2006/10/29 00:59:00  454          453.9993056 <- XXX
2005/08/01  2006/10/29 02:01:00  454          454.0840278 <- ok
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use strict;
use warnings;


use POSIX qw( difftime mktime strftime );
use Time::Local qw( timegm timelocal );
use Date::Calc qw( Delta_Days );


use constant ONE_DAY_IN_SECS => 24 * 60 * 60;


sub baseline {
   my ($then_date_str, $now) = @_;

   my ($y1, $m1, $d1) = $then_date_str =~ /^(\d{4})(\d{2})(\d{2})\z/;

   my ($y2, $m2, $d2) = (localtime($now))[5,4,3];
   $y2 += 1900;
   $m2 += 1;

   return Delta_Days($y1, $m1, $d1,
                     $y2, $m2, $d2);
}


sub bald_penguin {
   my ($then_date_str, $now) = @_;

   my @then = $then_date_str =~ /^(\d{4})(\d{2})(\d{2})/;
   my $then = mktime(0,0,0,$then[2],$then[1]-1,$then[0]-1900);

   return difftime($now, $then) / ONE_DAY_IN_SECS;
}


{
   print("Then        Now                  Date::Calc   BaldPenguin\n"
+);
   print("----------  -------------------  -----------  -----------\n"
+);

   for (
      [ '20050801', timelocal(0, 59, 0, 29, 10-1, 2006) ],
      [ '20050801', timelocal(0, 1,  2, 29, 10-1, 2006) ],

   ) {
      printf("%s  %s  %3d          %3d          %11.7f\n",
         do { my ($y, $m, $d) = $_->[0] =~ /^(\d{4})(\d{2})(\d{2})\z/;
+ sprintf("%04d/%02d/%02d", $y, $m, $d) },
         strftime('%Y/%m/%d %H:%M:%S', localtime($_->[1])),
         baseline(@$_),
         bald_penguin(@$_),
      );
   }
}
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