#! /bin/sh

b=`date +%b` # Locale's abbreviated month name.
e=`date +%e` # Day of month [1,31]; single digits are preceded by a space.
m=`date +%m` # Month number [1,12]; single digits are preceded by 0.
Y=`date +%Y` # Year, including the century (for example 1993).
tab="	"    # The tab character.
case ${#} in
   2)
      column=0
      month=${1}
      year=${2}
      ;;
   1)
      column=`expr \( ${m} - 1 \) % 3 + 1`
      year=${1}
      ;;
   0)
      column=0
      ;;
esac
if [ -z "${year}" -o "${year}" = "${Y}" ] ; then
   E="`tput smso`${e}`tput rmso`"
   case "${column}" in
      0)
         sedscript="
            /${b}/,/^${tab}/s/^${e}/${E}/
            /${b}/,/^${tab}/s/ ${e}/ ${E}/
         "
         ;;
      1)
         sedscript="
            /${b}/,/^${tab}/s/${e}\( .*  .....................  \)/${E}\1/
         "
         ;;
      2)
         sedscript="
            /${b}/,/^${tab}/s/^\(.....................  .* \)${e}\( .*  .....\)/\1${E}\2/
         "
         ;;
      3)
         sedscript="
            /${b}/,/^${tab}/s/^\(.....................  ....................  .* \)${e}/\1${E}/
         "
         ;;
   esac
fi
cal "${@}" | sed "${sedscript}"