Shell Programming and Scripting

#!/bin/sh
########### date2jd function ############
date2jd() {
 integer ijd day month year mnjd jd lday
        year=$1
        month=$2
        day=$3
        echo $year
        echo $month
        echo $day
        ((standard_jd = day - 32075 
           + 1461 * (year + 4800 - (14 - month)/12)/4 
           + 367 * (month - 2 + (14 - month)/12*12)/12 
           - 3 * ((year + 4900 - (14 - month)/12)/100)/4))
        ((jd = standard_jd-2400001))
 echo $jd
        return 0
}
########### user defined date ###########
echo 'Enter date in the format dd/mm/yyyy'
read DATE
DD=`echo $DATE | cut -c1-2`
MM=`echo $DATE | cut -c4-5`
YYYY=`echo $DATE | cut -c7-10`
####### current date ############
DD2=`date '+%d'`
MM2=`date '+%m'`
YYYY2=`date '+%Y'`
jd1=$(date2jd $YYYY1 $MM1 $DD1) || exit $?
jd2=$(date2jd $YYYY2 $MM2 $DD2) || exit $?
((jd3=jd2-jd1))
  echo $jd3

echo $year >&2

echo 'Enter date in the format: dd mm yyyy'
read DD MM YYYY XSTR

echo 'Enter date in the format: dd/mm/yyyy'
IFS="/" read DD MM YYYY XSTR
echo "$DD - $MM - $YYYY"