use Date::Parse; 
my $day = 24*60*60;
my $x = 3; # set this.
my $xdays = $x * $day;  
print scalar localtime(str2time("20121231") + $xdays);

##</code><code>##

use Date::Parse;
my $date = "20120516";
my $day = 24*60*60;
my $x = 24; # set this.
my $xdays = $x * $day;

# see perldoc -f localtime.
my @t = (localtime(str2time($date) + $xdays))[5,4,3];
$t[0] += 1900;  # localtime returns years since 1900.
$t[1] += 1;     # localtime returns month in range 0..11.

printf "%04d%02d%02d\n", @t;