day_of_week=$(date +%w)  # (0..6); 0 is Sunday, 5 is Friday
day_of_month=$(date +%e) # space padded
if [ ${day_of_week} -eq 5 -a ${day_of_month} -ge 15 -a ${day_of_month} -le 21 ]
then
   echo "third Friday "
fi

typeset -i mMth=1
mYear='2007'
while [ ${mMth} -le 12 ]
do
  m3Friday=`cal ${mMth} ${mYear} | tail +3 | cut -c16,17 | sed '/^ *$/d' | sed -n '3p'`
  echo "Third Friday of "${mMth}"/"${mYear}" = "${m3Friday}
  mMth=${mMth}+1
done

cal 05 2007 | sed -n "5{s/ *[0-9]\{2\}$//;s/^.* //p;}"

$ cal 12 2007
       December 2007      
Sun Mon Tue Wed Thu Fri Sat  
                         1
 2   3   4   5   6   7   8
 9  10  11  12  13  14  15
16  17  18  19  20  21  22
23  24  25  26  27  28  29
30  31

$ cal 12 2007 | tail +3 | cut -c16,17 | sed '/^ *$/d' | sed -n '3p'
 2
$ cal 12 2007 | cut -c16-18 | tail -4 | head -1
 13
$ cal 12 2007 | sed -n "5{s/ *[0-9]\{2\}$//;s/^.* //p;}"
14
$

$ cal 12 2007 | awk 'NR>2 && NF>=2 && ++w==3 {print $6}'
21
$ cal 07 2007 | awk 'NR>2 && NF>=2 && ++w==3 {print $6}'
20
$ cal 6 02007 | awk 'NR>2 && NF>=2 && ++w==3 {print $6}' 
15
$

count=0
month="05"
for s in `seq 1 31`
do
 fr=$(date +%a --date="2007-$month-$s" )
 if [ "$fr" == "Fri" ];then
     friday[$count]=$s
     count=$((count+1))
 fi 
done
echo ${friday[2]} #third fri