I'm learning how the relative pronoun when works in a sentence. While combining this clause
The day was snowy. My brother was born on that day.
I came up with 2 forms of relative adjective clauses.
I thought the first one was ungrammatical, but when I checked the sentence using QuillBot, it reflected that the sentence has no grammar error.
Are there any difference between the 2 sentences? [Edited]
Your second sentence is fine. The relative clause ("when my brother was born") is adjacent to the nominal that it modifies ("the day").
Your first sentence moves the relative clause away from the nominal that it modifies. That is a bit unusual but allowed in certain contexts, especially when the relative clause is lengthy. (It is sometimes called "extraposition from a noun phrase". The Wikipedia article on extraposition calls this the "standard case".) However, it sounds awkward here because "when" introduces adverbial clauses more often than relative clauses. Thus, the clause might seem to modify "was" instead of "the day". That is why sentence 2 sounds better than sentence 1 even though both are grammatically correct.
Both sentences are correct.
The first sounds a bid odd, maybe poetic. The second is natural.
This is probably because the clause "when my brother was born" seems to modify the noun "day", so it makes sense to have the clause right after the noun, but in your first sentence, you have "was snowy" in between.
If we replace "the day" with "it", it feels more clear that the "when"-clause modifies "the day was snowy":
It was snowy when my brother was born.
This is both correct and natural.
