cron

$ crontab -e

# m  h  dom mon dow   command
  0  2  *   *   0     sh /sh/sysbackup.sh
  0  8  *   *   1-5   sh /sh/iptables_block.sh
  0  17 *   *   1-5   sh /sh/iptables_open.sh

$ sudo select-editor

string         meaning
------         -------
*/5 * * * *    Run every 5 minuets.
5   * * * *    Run at the 5th minute of the hour.
@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 * * * *".