The behaviour of jeder is well discribed herehere. If you don't understand everything there just look at the first table.
According to that, jeden is the accusative form of jeder, not the dative.
So you can't decide in general if it is jeden Abend or jeder Abend, it depends on the function of Abend in this sentence: is it subject, dative object, accusative object?
Here are some examples:
Every evening is the same.
Jeder Abend ist gleich.
Every evening we do the same.
Jeden Abend machen wir das Gleiche.
An jedem Abend machen wir das Gleiche.
To learn more about this topic you might look into general German grammar. For a first glance you might take thisthis and replace every article with the respective form of jeder. This works perfectly fine, even if some sentences don't really make sense anymore ;)