To configure the wifi on an OpenWrt One to turn off at 10PM and on at 6AM, modify the crontab to be:

0 22 * * * uci set wireless.radio0.disabled=1; uci set wireless.radio1.disabled=1; wifi
0 06 * * * uci set wireless.radio0.disabled=0; uci set wireless.radio1.disabled=0; wifi

This can be done by SSHing into the router as root. I configured my One to be on IP address 192.168.1.2 since I have a router/firewall on 192.168.1.1.

ssh root@192.168.1.2

And then run the following to set up the crontab and to start cron:

echo "0 22 * * * uci set wireless.radio0.disabled=1; uci set wireless.radio1.disabled=1; wifi" >> /etc/crontab
echo "0 06 * * * uci set wireless.radio0.disabled=0; uci set wireless.radio1.disabled=0; wifi" >> /etc/crontab
/etc/init.d/cron enable
/etc/init.d/cron start
/etc/init.d/cron restart

Copied from instructions on the OpenWrt forum