Author here. It's answered briefly in the FAQ

> In casual benchmarks, the pure-Python version is about 10x slower than the Rust version, making it 5x slower than the standard library but still (in general) faster than Pendulum and Arrow.

"(in general)" here since the speed compares differently per operation, while the Rust version is faster across the board. That said, there's no operation that is _significantly_ (or unnecessarily) slower than Arrow or Pendulum.

edit: I'm considering adding comparison to the pure Python version once I get the time for a more expanded "benchmarks" page in the docs

Thank you. My apologies for not reading the FAQ. Also thank you for sharing your library.

No problem. After all, the readme does go from mentioning Pure Python directly to showing a benchmark graph where it's curiously absent