Simple English sentences, help me see which one is wrong.

The first sentence is wrong. Today should be changed to daytime.

First of all, fine is an adjective, adjectives can only modify nouns, and adjectives can only modify adjectives in specific occasions. Look at today, this is an adverb of time. You can't modify it with adjectives, so today should be changed to day. Because day is a noun, it can be modified with adjectives.

I hope it helps you! ~