Code:

#! /bin/sh
set -x
YEAR=`date +"%Y"`
NMONTH=`date +"%m"`
DATE=`date +"%d"`
if [ $DATE -eq 01  ];then
case $NMONTH in
01|02|04|06|08|09|11)
       DATE=31
        if [[ $NMONTH == "01" || $NMONTH == "1" ]]; then
                YEAR=`expr $YEAR - 1`
                NMONTH=12;LMONTH="December"
        else
         NMONTH=`expr $NMONTH - 1`
        fi;;

03)     if [[ `expr $YEAR % 4` -eq  0 ]]; then
                DATE=29
        else
                DATE=28
        fi
        NMONTH=`expr $NMONTH - 1`;;
*)
        DATE=30
        NMONTH=`expr $NMONTH - 1` ;;
esac
else
       DATE=`expr $DATE - 1`
      echo $DATE
fi
if [ ${#NMONTH} -eq 1 ]; then
  NMONTH="0$NMONTH"
fi
if [ ${#DATE} -eq 1 ]; then
 DATE="0$DATE"
fi
case $NMONTH in # set long month name
01)     LMONTH="January";;
02)     LMONTH="February";;
03)     LMONTH="March";;
04)     LMONTH="April";;
05)     LMONTH="May";;
06)     LMONTH="June";;
07)     LMONTH="July";;
08)     LMONTH="August";;
09)     LMONTH="September";;
10)     LMONTH="October";;
11)     LMONTH="November";;
12)     LMONTH="December";;
esac
echo $DATE-$NMONTH-$YEAR #Output date-month-year



the o/p that i am getting is 
 

Code:

+ date +%Y
YEAR=2010
+ date +%m
NMONTH=07
+ date +%d
DATE=14
+ [ 14 -eq 01 ]
+ expr 14 - 1
DATE=13
+ echo 13
13
date bad substitution