Shell Scripting - Generate date string values

generate-dates-for-last-month.sh

# This script generate comma separated dates for last month in yyyy-mm-dd format.
# Ex:  
#     "2018-04-01,2018-04-02,2018-04-03,2018-04-04,2018-04-05,2018-04-06,2018-04-07,
#      2018-04-08,2018-04-09,2018-04-10,2018-04-11,2018-04-12,2018-04-13,2018-04-14,
#      2018-04-15,2018-04-16,2018-04-17,2018-04-18,2018-04-19,2018-04-20,2018-04-21,
#      2018-04-22,2018-04-23,2018-04-24,2018-04-25,2018-04-26,2018-04-27,2018-04-28,
#      2018-04-29,2018-04-30"
set `date +%m" "%Y`

CURMTH=$1
CURYR=$2

if [ $CURMTH -eq 1 ] 
then 
    PRVMTH=12
    PRVYR=`expr $CURYR - 1`
else 
    PRVMTH=`expr $CURMTH - 1`
    PRVYR=$CURYR
fi

if [ $PRVMTH -lt 10 ]
then PRVMTH="0"$PRVMTH
fi

LASTDY=`cal $PRVMTH $PRVYR | egrep "28|29|30|31" |tail -1 |awk '{print $NF}'`
FROM_DATE="$PRVYR-$PRVMTH-01"
TO_DATE="$PRVYR-$PRVMTH-$LASTDY"

# convert in seconds sinch the epoch:
start=$(date -d$FROM_DATE +%s)
end=$(date -d$TO_DATE +%s)
cur=$start

while [ $cur -le $end ]; do
# convert seconds to date:
REPORT_DATE=$REPORT_DATE$(date -d@$cur +%Y-%m-%d)",";
let cur+=24*60*60
done

# Remove last comma (,)
REPORT_DATE=${REPORT_DATE::-1}
echo $REPORT_DATE;

generate-dates-from-today-till-start-of-the-month.sh

# This script generates the dates from today till the start of the month in yyyy-mm-dd format.
# Ex. If current date is 2018-05-03 then it will generate "2018-05-01,2018-05-02,2018-05-03".
set `date +%m" "%Y`

CURMTH=$1
CURYR=$2
CURRENT_DATE=`date +%d`;
FROM_DATE="$CURYR-$CURMTH-01"
TO_DATE="$CURYR-$CURMTH-$CURRENT_DATE"

# convert in seconds sinch the epoch:
start=$(date -d$FROM_DATE +%s)
end=$(date -d$TO_DATE +%s)
cur=$start

while [ $cur -le $end ]; do
    # convert seconds to date:
    REPORT_DATE=$REPORT_DATE$(date -d@$cur +%Y-%m-%d)",";
    let cur+=24*60*60
done

# Remove last comma (,)
REPORT_DATE=${REPORT_DATE::-1}
echo $REPORT_DATE;