Translate decimal into date

Hello,
what can I do to convert a decimal number (001-366) into the day of the year it represent in the format of mm-dd-yyyy ?
I know about the date +%j, it gives me the number for the current date, what about a reverse of this, is there such a thing?
My number resides in a var, what can I do to obtain the date it represents?

Thanks!

With the GNU version of the command date :

$ julian=217
$ jdate=$(date -d $julian +'%d/%m/%Y')
$ echo $jdate
05/08/2009
$

Jean-Pierre.

Thanks, but I am using ksh88.
I could use perderabo's datecalc, it works great (thanks to perderabo for all of it), I was just exploring the possibilities of getting the result via built in functionality.
Thanks again.

Gio001, ksh88 is a very old version of the Korn Shell. If you upgrade to ksh93, it has excellent build-in date arithmetic support amongst other major enhancements.

To use Aigles example where the DOY is 217.

$ printf "%(%D)T\n" 217
08/05/09

His output is in DD/MM/YY format. Mine, since I am in North America is in MM/DD/YY format.