[shun]

Originally Posted by muaz

Because my teacher says that we can use present tense for future too.
for instance: " I am going to fly tomorrow."
It is in present tense but about future.

I have said something like the following, and I think it is the main point relating to your question.

Old criterion for Future Tense is future time, and it is a wrong criterion. This old erroneous criterion will lead to the doubt of existence of Future Tense. Nowadays, some people even say there is no Future Tense.

Claiming there is the Future Tense, I therefore suggest the criterion for Future Tense should be whether certain or uncertain. If uncertain, even a present action can be described in Future Tense:
Ex: John will be in his office now.

If the action is certain, however, even a so-called future action is described in present tenses, Simple Present or Present Progressive:
Ex: We go to Europe tomorrow/next weekend.
Ex: We are going to Europe tomorrow/next weekend.
== Just because there is Future Tense "will go" that indicates an uncertainty, here we deliberately use present tenses to throw a contrast with Future Tense. Present tenses here say these actions are a certainty, even with future time expression.
Nevertheless, unfortunately, these examples have been mistaken by people as an evidence to prove against Future Tense, and they concluded there is no Future Tense.
Because their old erroneous criterion on Future Tense is future time, these examples having violated their criterion are taken as a denial to the existence of the Future Tense.

But you should read more, if you tolerate linguistic discussion. Future Tense is very complicated and here is only a small part of its use. Believe it or not, I am here proving there is Future Tense. You may give your opinions here.