A relative adverb refers to or stands for an adverbial and something that stands for an adverbial is an adverbial itself. That is always like that. A pronoun for instance, stands for a noun and is therefore a noun as well. Sometimes it can be difficult to distinguish between the relative adverb quando / when and the temporal conjunction quando / when. In the following sentence for instance quando / when is a temporal conjunction. Quando / when doesn't refer to adverbial of time, because there is none.
Eu não sei
I don't know
The easiest way to distinguish between a temporal clause and a relative clause is to delete the relative clause. If the result is a grammatically correct sentence, it is a relative clause, although the meaning may be altered completely. In a sentence like "All times once passed are good" we can leave out, see the following table, "once passed". The remaining sentence "All times are good" is grammatically correct and nobody has the impression that something is missing. If we leave out the temporal clause in "I don't know when he comes" we get "I don't know" and this sentence is incomplete, because it is unclear what he doesn't now.
All times once passed are good.
The weeks his health allows it, he accompanies us.
Already during the day when the body consumes more energy it is important that the meals complies the consumption.
olhares* para trás, verás que os dias mais belos foram aqueles em que lutaste.
you look back you will see that the best days were the days you stand up for something.
the sun shines, the secretion of melatonin is reduced.
14 pessoas foram mortas este domingo
um carro carregado de explosivos explodiu num cruzamento.
14 persons died this sunday
loaded with explosives exploded on a crossroad.
The relative adverb should not be confused with the temporal conjunction. (Actually from a practical point of view it is completely irrelevant to see the difference, although perhaps in some circumstances it can be useful to be able to distinguish between the relative adverb and the conjunction.)
Quando can mean as well while.
Perco a noção do tempo
I lose any sense of time
while / when
I am writing.
The adverb quando can introduce a restrictive relative clause, a nonrestrictive relative clause.
non restrictive relative clause
Saturday, when we made a trip to the coast, the sun was shining.
restrictive relative clause
Today was the day the United Kingdom decided to dissociate itself from the European project.
Everything here recalls to my mind the days when I lived inside the country.
direction of travel
The day Sweden changed the direction of travel of all its streets.