With the current conquest mechanics, keeping track of port timer for defense and attack is vitally important. I'm adding to this post a few links that will help with that.

Interactive maps with port timers:
TDA-map - shows timers and Lord Protector's for all ports except the secret islands.
TDA-map 2 - essentially the same map, but also indicates visually the time left till each port opens up for attack

Port timer statistics
mdb-dev - shows how many ports each nation holds and lists them according to their respective timers