Works here,

$ perl -e '$mtime=(stat("new_folder"))[9];
@date=localtime($mtime);
$date[5] +=1900;
$date[4] +=1;
print "$date[5]-$date[4]-$date[3] $date[2]-$date[1]:$date[0]\n";'
2009-8-28 14-19:27
$ touch new_folder/test.file
$ perl -e '$mtime=(stat("new_folder"))[9];
@date=localtime($mtime);
$date[5] +=1900;
$date[4] +=1;
print "$date[5]-$date[4]-$date[3] $date[2]-$date[1]:$date[0]\n";'
2009-8-28 14-19:46
[download]

What OS, which Perl etc..