Convert Date format in Unix (ddmmyyyy to dd-mon-yyyy )

Could not find an inbuilt function in unix to convert ddmmyyyy to dd-mon-yyyy format.So wrote this script. Check this out.

month_mon='JAN+FEB+MAR+APR+MAY+JUN+JUL+AUG+SEP+OCT+NOV+DEC'
time_stamp='01012007' #&1
dd=`echo $time_stamp (pipe) cut -c5-6`
mm=`echo $time_stamp (pipe) cut -c3-4`
yy=`echo $time_stamp (pipe) cut -c1-2`
file_mon=`echo ${month_mon} (pipe) cut -d"+" -f${mm}`
file_date=$file_dd'-'${file_mon}'-20'${file_yy}
echo $file_date

NOTE: The pipe symbol before cut is getting filtered out in this blog. Please take care to replace (pipe) with the actual one.