for_date_loop.sh

set -ex

# method 1
# [2020-01-01, 2020-01-31]
for i in {0..30}; do 
    thedate=$(date -I -d "2020-01-01 +$i days")
    echo $thedate
done

# method 2
start_date="2020-05-01"
end_date="2020-05-31"
end_date=`date -d "-1 days ago $end_date" +%Y-%m-%d`  # include end_date
while [ "$start_date" != "$end_date" ]; do
    echo $start_date
    start_date=`date -d "-1 days ago ${start_date}" +%Y-%m-%d`
done