I think the difference is that one event is a statement about the present which is either presently true or not, and the other is a prediction. So you could illustrate the difference by using the following pairs: P(Mom on phone now) vs. P(Mom on phone tomorrow at 12:00am). In the dice case P(die just rolled but not yet examined is 1) vs. P(die I will roll will come out 1).

I do agree with Oscar though, the maths should be the same.