my $sth_prepare = $dbh1->prepare("select datestamp, count(id) from userlog group by substring(datestamp,1,10) order by datestamp asc limit 0,12");
$sth_prepare->execute() or die $DBI::errstr;

my $day_now;
my $day_old;
my $dif = 1;
my @dif_array = ();

while (my @arr2 = $sth_prepare->fetchrow_array()) {
   $day_now = substr($arr2[0],8,2);
   $dif = $day_now - $day_old;
   push @dif_array, $dif;
   for (@dif_array) {
      push @array, 0 if $_>1;
   }
   push @array, $arr2[1];
   $day_old = $day_now;
}