On the dictionary, it says that to refer to "tomorrow" (the next day), we should use "mañana" as an adverb. If we use "mañana" as a noun, it would mean "morning" or "future". However, is there any case where "mañana" as a noun can refer to "tomorrow"?
Like in the following sentence (source):
El partido de fútbol es mañana. (The football game is tomorrow.)
It seems that the word "mañana" is at the object position. Why is it still an adverb? If it is an adverb, what is the object of this sentence?
Similarly, in the following sentence:
Mañana será otro día. (Tomorrow will be another day.)
It seems that the word "mañana" is at the subject position. Is it because it is actually saying "(It) will be another day tomorrow."? Or is it referring to the figurative tomorrow so that "Mañana" is actually a noun here? Would it be equally valid to say "Será otro día mañana."?