sudo apt-get update
sudo apt-get install cron

sudo /sbin/chkconfig crond on
sudo /sbin/service crond start

crontab -e //for editing
crontab -l //list of jobs

Syntax:

* * * * * echo ‘Run this command every minute’ >> file.log
5 * * * * curl http://www.google.com
0 3 15 * * /home/backup/backup.sh //every 15th 3AM

https://www.digitalocean.com/community/tutorials/how-to-use-cron-to-automate-tasks-on-a-vps