Student or Learner
"My girlffriend and I have been together for 2 years next month."
Would it be acceptable to say "My gilfriend and I have been together for 2 years on July 2nd next month."?
Please note that I'm not a teacher.
The reason, of course, is that next month is in the future, while today is the present.
So future perfect for next month, present perfect for today.
In practice you could say this: "My girlffriend and I have been together for 2 years - on July 2nd next month." That is, you are using the present perfect (meaning the 2 years has been completed), and then clarifying that it's not quite 2 years yet.
Similarly, compare "I am 21 years old next Monday" with "I'll be 21 years old next Monday."
The first is colloquial, but for formal and academic purposes, and when precision and logic are needed, you should use the second form.
At least that is my opinion.