I noticed from some1 Books output some entries(example) where "now" and "then" are used as adverbs to compare something now with something then(not unlike "before and after"); or to identify a period of time when events related to a person/topic/place unfold. Often this appears within titles and is followed by a colon:
[a person/topic/place] Now and then: the journey from Z to A/a review of an era in the field of strange... etc.
Obviously in context this doesn't mean "occasionally". At the same time it seems to "mean a lot" with very little, so to speak, as in it's shorter/simpler than since then until now, and the order is not chronological as it would be with then and now.
Is that simply considered the literal meaning of those adverbs modifying the preceding noun? Or is that some kind of competing "idiom" as in "the now and the then" of something; are those two adverbs some kind of group ? Why is the preposition "of" not required between the noun and "now and then"; and why isn't the syntax rather "Now and then: [a person/topic/place], the journey... etc."?