- I am your math teacher this week / month / year.
- I will be your math teacher this week / month / year.
- I have been your math teacher this week / month / year.
While the first sentence can be uttered at any time of this week / month / year, what about the second and third?
I feel that the second can be only said at the first day or first class of this week / month / year. The 3rd sentence can be said after the middle of this week / month / year.