Two flawed assumptions;

1) Omniscience is a contradiction. Knowledge is a function of subjectivity. What if you have a camera and you set the shutter speed to 10 minutes. Obviously you get much more information from all the light, but it starts to cancel out and all you get is a whiteout.

any knowledge is a function of its context. We are reductionist, as we have to distill the signal from the noise, but the noise is context for the signal. Once you start pulling the fabric apart, it becomes a different fabric.

2) What determines is process and process has to occur. We are mobile organisms, necessiating this sequential process of perception, in order to navigate, so we think of time as a sequence of events. Yet time is not so much the present moving past to future, as it is change, turning future to past. Tomorrow becomes yesterday, because the earth turns.

There is no literal dimension of time, because the past is consumed by the present, to inform and drive it. Causality and conservation of energy. Cause becomes effect.

Consequently the process of determination can only occur as the present. The future is potential because it has not been determined and the past is residual, because the energy which manifested it has transitioned beyond it.

Of course, free will is also an oxymoron, as a will free of cause would be eqully free of effect and the premise of will is to affect. We are a small part of nature's process of selection.