ciso8601 is blazingly fast, and also its wall time is very stable. By all means, use ciso8601 if the format allows :)

On my machine, ciso8601 always runs in 240ns, and the Rust lib median time is 1250ns.

You can run a benchcmark too! Just call pytest, and it will generate an .svg report: https://github.com/gukoff/dtparse/blob/master/tests/test_per... (you'll need to pip install ciso8601 pytest pytest-benchmark[histogram])