About crone service

I want to know about ….cron service………I wat to change my iptables rules at specific times…..So how can i add it into my cron services..i want to do it daily 1.00 pm…. I have created 2 iptable files….with two different rules….am trying to restore the two files using cron service at two different times…… but its not working ,,,,, I am adding my crontab configuration below… 0 13 * * * iptables-restore /etc/sysconfig/iptables 30 13 * * * iptables-restore /etc/sysconfig/iptables2 I am using Fedora Core9….I have checked everything. Crone service is started…… Anybody can find a soultion…….please help me…….