bash script that reschedules it self to run at random time in crontab

auto_reschedule_cron.sh

#!/usr/bin/env bash
# Script that reschedules is self in crontab
# Should be added to crontab manually first
# Also add/call the "real job" (actual program) you want to run in crontab

# Comes with NO warranty, use at your own risk!

# Max range for added random time
days=30
hours=10
mins=59

# Get current cron jobs
cron=$(mktemp)
crontab -l > $cron
# Generate new random date
new_date=$(date -d "now + $((RANDOM % $days)) days $((RANDOM % $hours)) hours $((RANDOM % $mins)) minutes" +"%M %H %d %m * ")
# Update cron file
sed -i "s%.*$0%$new_date $0%g" $cron
# To apply might need -f switch depending on crontab version
crontab $cron

# Clean up temp
rm -f $cron

Based on answer and ideas from this stackoverflow question:
https://stackoverflow.com/questions/9049460/cron-jobs-and-random-times-within-given-hours