You can set crontab to run cron once a day every day. The format is:
minute hour * * * command
Replace the minute and hour for the time that you want your cron job to run every day. Command is the script or command that you would like to run by cron. For example:
30 23 * * * backup.sh
Per this entry, cron will run backup.sh at 23:30 (11.30pm) once a day, every day.