#Aide Crontab
#
┌────────── minute (0 - 59)
│ ┌──────── hour (0 - 23)
│ │ ┌────── day of month (1 - 31)
│ │ │ ┌──── month (1 - 12)
│ │ │ │ ┌── day of week (0 - 6 => Sunday - Saturday, or 1 - 7 => Monday - Sunday)
│ │ │ │ │
↓ ↓ ↓ ↓ ↓
* * * * * command to be executed
58 23 * * * /sbin/iptables-save > /etc/firewall.iptables-cron 2>&1
string meaning
------ -------
@reboot Run once, at startup.
@yearly Run once a year, "0 0 1 1 *".
@annually (same as @yearly)
@monthly Run once a month, "0 0 1 * *".
@weekly Run once a week, "0 0 * * 0".
@daily Run once a day, "0 0 * * *".
@midnight (same as @daily)
@hourly Run once an hour, "0 * * * *".
#####
Hope it will help ;)