- I will send you my proposal two months before the exam date.
- I will send you my proposal two months before the exam day.
Which one is more correct?
- I will send you my proposal two months before the exam date.
- I will send you my proposal two months before the exam day.
Which one is more correct?
As Jim said, both variations are acceptable, and they are functionally interchangeable.
Stylistically, I prefer date over day in the relatively formal context of your example sentence. Here's what sounds most natural to my ears:
I will send you my proposal two months prior to the exam date.
Again, both of your original examples are grammatically correct. I'm just musing on nuances of style here.
Something else to consider: in your example, "exam date" and "exam day" are basically interchangeable as the objects of a preposition. They barely differ. However, it's less simple when we cast them as the SUBJECT of a clause/sentence. "Exam day" is acceptable (similar to game day, Christmas day, graduation day, even Monday & today) and is interchangeable with "the day of the exam".
On the other hand, "exam date" does not work as a sentence subject; instead, you could say "the date of the exam", but note the difference in meaning ("date" = the calendar number, "day" = the occasion/event).