Basically the title, you need to use the skills you have now and be a productive member of society.
I don’t mean go back and show the wheel or try invent germ theory etc.
For example I’m a mechanic i think I could go back to the late 1800s and still fix and repair engines and steam engines.
Maybe even take that knowledge further back and work on the first industrial machines in the late 1700s but that’s about it.
As a waitress, probably the 1980’s.
As a computer scientist / CS teacher, probably the 1960’s… without being outed as a time traveler, anyway.
I’m not sure how well they did in the past, but surely mathematicians / math teachers are a thing.
Someone who knows a bunch of complexity theory, graph theory, and sorting algorithms for large data sets; but not calculus or set theory is gonna be conspicuously unusual the further back you go.
But only for about 500 years, then you’re a madman or a witch and things get really interesting.
My computer science curriculum covered calculus - perhaps not as rigorously as the mathematical sciences, but enough for it to be working knowledge (personally, I’ve forgotten 90% of it since graduation).
Plus, I am sure a computer science teacher should be at least familiar with these topics, or be capable of picking them up.
I’m familiar, I could pick them them up (I have before, and like you, forgotten them from disuse), but I certainly don’t know them offhand the way I know, say, Dijkstra’s algorithm.