Why do all the English translations use this totally-artificial order? No native speaker would ever utter an atrocity like "During the day you arrive at the temple". In the unlikely event that we'd want to express this thought, we'd say "You arrive at the temple during the day". English is an SVO language.
Actually, we often find a prefix on the verb (like the ad- here, on advenis) "repeated" in the preposition in the same sentence; they liked it, apparently.
In any case, a verb of motion, like advenis, can't govern a direct object; "You arrive at the temple." You can't 'arrive the temple' (the way you could build the temple, or destroy the temple, or see the temple). There has to be a preposition (like ad = to) that gets you from the verb to the place.
You could say, in English, "You reach the temple," and that would be an accurate translation of this Latin sentence (Ad templum advenis ); however, it would use a direct object ("the temple") instead of a prepositional phrase (the Latin ad templum ).
It is a feature of Latin, that the prefix on the verb and the preposition used in the same sentence, are often 'the same' word. My feeling is that they liked and appreciated the unity provided (what I was calling "repetition").
There's no ad + dative; whatever the meaning of ad (whether "to/toward" or "at" or "for (a purpose)"), it is always followed by the accusative case.
They sit at the door = Ad iānuam sedent.
They run to the tree = Ad arborem currunt.
They call us to dinner = Ad cēnam nōs vocant.
The dative, alone, with no preposition, is used to mean "to/for" when designating a recipient:
I tell Marcus a story = Marcō fābulam nārrō .
They give the captives to Caesar = Caesarī captīvōs trādunt .
(Notice that, in English, we have the choice of using "to" for the dative ( = indirect object) of of leaving it out:
I give him the book = I give the book TO him. )