Based on: *te-, *to-
We'll learn how to properly arrange actions (clauses) in time using the German words for before, after and while. Also: difference between nachdem and danach and others
bevor, vorher, danach, nachdem, während
It’s the core of words like the, there, then and so on.
English etymological sources mention the root as *so-, while German ones spell it with “t”, but it’s in essence the same.