Perl provides all the directory and date info you require. The following works for me, as well as testing for existence, in anything other than a command line hack such as below, you should also test the return value of the mkdir commands.

On a Unix system you cannot create a whole path with a mkdir command, unless you supply the -p option, but as I said, when Perl provides the means to create directories and test the outcome of the request, why spawn a shell sub process ;)

 
utilitarian@busybox:~/tmp/test$ perl -e '
$time=localtime;
($day,$month,$date,$time,$year)=split(/ /,$time);
$stamp=$year."_".$month."_".$date;
$dir="result_".$stamp;
mkdir "results" if ( ! -d "results");
$path="results/$dir";
mkdir "$path" if ( ! -d "$path");
open (F,">>", "$path/results.log");
print F "This file exists\n";
close(F);'
utilitarian@busybox:~/tmp/test$ ls results/
result_2009_Jun_17
utilitarian@busybox:~/tmp/test$  ls results/result_2009_Jun_17/
results.log
utilitarian@busybox:~/tmp/test$  cat  results/result_2009_Jun_17/resul
+ts.log
This file exists
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