The Perception range modifier allows your attacks to hit anything you can sense. Postcognition lets you see backwards in time and Precognition lets you see forward in time. Can you use this to attack people in the past/future without any risk to yourself?
Compare the Dimensional modifier, which can be applied to Senses or powers to allow you to target another dimension with relative safety. I suspect that you would need to have a similar Extra on your power to be able to apply them to the past or the future that you are viewing. But past that, it's really not that much different than uses of Dimensional.
On the other hand, this does also require some meditation on the nature of the past and the future in your particular world. Can the past be changed? Does it affect the present? Is the future that you access with your powers a defined future that will happen no matter what happens in the present (or the past)? Depending on how this works, attacking targets in the past and the future could be a devastating sneak attack, or be the equivalent of mental masturbation with it only having an effect in your mind.
This does also get into some questions on how Perception works without a direct link. A classic case brought up in 2e was whether Darth Vader could force choke through a video screen, but you get odder cases like if the person transmitting is doing so on a green screen (you don't know the location) or using an avatar (you don't know the person). Similar problems for Teleport, but it all comes down to descriptor.