#!/usr/bin/perl
use strict;
use warnings;
use Time::Local;

my $timestamp1 = 1143151500;
my $differenzTage = 7;

my $timestamp2 = $timestamp1 + $differenzTage * 86_400;

printf "   Erstes Datum: %s (%d s)\n", scalar localtime($timestamp1), $timestamp1;
printf "%3d Tage später: %s (%d s)\n", $differenzTage, scalar localtime($timestamp2), $timestamp2;
__END__
   Erstes Datum: Thu Mar 23 23:05:00 2006 (1143151500 s)
  7 Tage später: Fri Mar 31 00:05:00 2006 (1143756300 s)