The Spanish translation of
He appears at night.
are given below. Is it correct both to say
Él aparece en la noche.
Él aparece a la noche.
a, what is the difference between the use of them?
I think both forms could be understood as correct, but a Spanish speaker would actually favor the prepositions
Él aparece de noche. La Luna sale de noche.
Él aparece por la noche. La Luna sale por la noche.
It is correct to say
... a la noche.
You can use the preposition
a + noun to designate parts of the day.
a la mañana, a la tarde, a la noche.
You can also use
... en la noche
since the preposition
en is used to indicate the time, place or way in which the action of the verb it goes with (in this case
aparecer) was performed. But, again, prepositions
por work better for this example.