The concert tomorrow.

The concert which is tomorrow

I thought Adverbs couldn’t modify nouns. Is the first an exception to the rule?

Tomorrow

–noun
1.    the day following today: Tomorrow is supposed to be sunny.
2.    a future period or time: the stars of tomorrow.
–adverb
3.    on the morrow; on the day following today: Come tomorrow at this same time.
4.    at some future time: We shall rest easy tomorrow if we work for peace today.