Yes. Someone hopes something is going to happen. That person hopes that "tonight is the night," definite article, the particular night, that it will happen. The 28th of August is the night when it will happen. Often it means the night that a couple is going to have their first romantic encounter.

tonight is going to be an important night? --- u are telling me that tonight is an important night tonight is going to be the night ... u are telling that tonight is the night that you have told someone about . Eg. Tonight is the night , bro What night what you talking about ??? Have you forgotten what i said a week ago about an important night > Oh , i see , so tonight is the night then ,huh?