My draft says:
Weyl wrote these words in 1925, since when a long torrent of mathematical development has surged under the bridge of time.
Unsure that the phrase "since when" is sufficiently acceptable in formal writing, I went to substitute the phrase "since which time"—except that, in this particular sentence, that doesn't work. (Reason: it inadvertently creates a false parallel, for the word "time" appears with different meaning in the same sentence.)
I don't actually like my sentence, which smacks of a freshman's attempt to overreach for eloquence. I mean probably to strike it out and write something different (as soon as I think of something different to write), but meanwhile I wonder: is "since when" actually wrong in such a use? If it is, since when?