The simple present tense is sometimes used to talk about the future. This, for example, happens when we are talking about events that are part of a timetable.

The second semester starts on September 15^th.
The train arrives at 3:30.
My plane is at five o’clock.
When does the train depart?

Subordinate clauses

The simple present tense is often used with a future meaning in subordinating clauses introduced by what, when, where, until, if and than.

I will call you if I have time. (NOT I will call you if I will have time.)
I will pay you back when I get a job. (NOT I will pay you back when I will get a job.)

The simple present tense is occasionally used with a future meaning when giving and asking for instructions.

Well, what do we do now? (OR What will we do now?)

In other cases, we do not usually use the simple present to talk about the future. Instead we use the present continuous or simple future.

I am visiting my parents tomorrow. (NOT I visit my parents tomorrow.)
I promise I will phone this evening. (NOT I promise, I phone you this evening.)