Code
# note proper parameter validation (e.g. mon between 1 and 12 inclusive)
# script also assumes that you have read/write access to all subdirectories

scriptname=$(basename $0)
if [ $# -ne 3 ]; then
  print "usage: $scriptname MonthNumber YearNumber directory, e.g. '$scriptname 4 2006 /tmp'"
  exit 0
fi

set -A monnames Zero Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
typeset -i mon=$1
typeset -i yr=$2
typeset -i thisyr=$(date +%Y)
typeset -i lastyr=$(($thisyr -1))
typeset -i thismon=$(date +%m)
typeset -i fmon

print "Print Deleting files from ${monnames[$mon]} $yr in directory $3"

find $3 -type f -ls | sed -e's/ *//' | tr -s ' ' | cut -d' ' -f8- | while read fmonname fday fyrtime ffilename
do

# Get month number from month name in file list
  fmon=1
  while :
  do
    if [ $fmonname = ${monnames[$fmon]} ]; then
      break
    fi
    fmon=$(($fmon + 1))
  done

# if the last part of the timestamp is a time rather than a yr then
# we need to find the yr it belongs to

  if [[ $fyrtime = *:* ]]; then

#   if month number is not greater than current month number then it is in this yr ...
    if [ $fmon -le $thismon ]; then
      fyrtime=$thisyr
    else

#     ... otherwise it's last yr
      fyrtime=$lastyr
    fi
  fi

  if [ $fmon = $mon ]&&[ $fyrtime = $yr ]; then
    print "deleting $fname dated $fday $fmon $fyrtime $ffilename"
    -- backup $ffilename somehow --
  fi
done
~