My Linux scripting is limited but try putting something like this in autostart.sh
#!/bin/bash
until $(curl --output /dev/null --silent --head --fail --max-time 5 http://google.com); do
sleep 20
done
ntpd -d -n -q -p europe.pool.ntp.org
It should hit google every 20 seconds until it gets a response then set the network time.