I was just searching for this. Before the Attack Planner got updated, you would receive a reminder that you had a launch time in 60 seconds. After it was updated, you no longer get the warning.
I'm a n00b. 1st time i used the attack planner i expected the attacks to be launched automaticly.. Appears you still have to launch manually at the time. Correct?
InnoGames is working on this as a bug now. Currently, you can get the notifications 60 seconds before departure time if you refresh your browser after editing the attack plans and also after each attack plan notification you receive.