bash script to delete opensprinkler logs more than a week old

deleteoslogs.sh

#!/bin/bash
# os wants dates in epoch time divided by 86400 (86400 = 1 day)
# we want to ensure that logs are only kept on the OS for a week, so get the epoch date one week ago and ask OS to delete logs for that day
epochdate=`date --date="1 week ago" +%s`
osdate=$((epochdate / 86400))
echo `date`: Deleting logs for `date --date="1 week ago"`: $epochdate / 86400 = $osdate >> /home/user/sandbox/os/log.txt
# replace ip address and [md5hashedpassword] with your opensprinkler's details  
curl -s "http://192.168.1.20:80/dl?pw=[md5hashedpassword]&day=$osdate" >> /home/user/sandbox/os/log.txt
echo >> /home/user/sandbox/os/log.txt