UNIX for Advanced & Expert Users

DATE1=01/11/2012
DATE2=10/12/2012

 for examples Sunday count between DATE1 and DATE2 is 
5

#!/bin/ksh

DATE1="$1"
DATE2="$2"
TMP1=`mktemp`

NDATE1=`date +%s -d "$DATE1"`
NDATE2=`date +%s -d "$DATE2"`

DIFFD=`echo "$NDATE2 - $NDATE1" |bc`

NUMDAY=`echo "$DIFFD / ( 60 * 60 * 24 )" | bc`
for ((i=1; i <= NUMDAY ; i = i + 1))
do
date --date="$i day" |grep  "^Sun" >> $TMP1
done

echo "Number of Sundays between $1 and $2 : `cat $TMP1|wc -l`"
rm -rf $TMP1

[root@#####]# sh dow.sh 2012-11-01 2012-12-10
Number of Sundays between 2012-11-01 and 2012-12-10 : 6

The following error :-
Invalid character in date/time specification.
Usage: date [-u] [+Field Descriptors]
Invalid character in date/time specification.
Usage: date [-u] [+Field Descriptors]
syntax error on line 1 stdin
syntax error on line 1 stdin
user.sh[13]: syntax error at line 13 : `(' unexpected

$ A=$(date +%j -d"11/01/12")
$ B=$(date +%j -d"12/10/12")
$ C=$(date +%u -d"11/01/12")
$ echo $(( (B-A)/7 + ((B-A)%7+C)/7 ))
6