To take off on Roy's great answer, the more common constructions use either the accusative or dative cases.
"Every evening we do the same." Here, there is an implied word, during. That's why "jed--" is not in the nominative case in German. Instead, there are two ways to render it.
An jedem Abend machen wir das Gleiche. We're using a preposition, "an," which makes jed--, jedem, putting it in the dative.
Jeden Abend machen wir das Gleiche. Here, jed-- is jeden, in the accusative, because there is no preposition.
Then there is the nominative example, Jeder Abend ist gleich. Every evening is the same. (There is no implication of "during.") So "Jeder Abend" remains in its "original" (nominative) form.