As noted in #16728 (comment) we don't currently test for older pandas <0.24 in CI (unless I missed it).

In readme we say that "a few examples require pandas >= 0.18.0" (released March 2016).

I suspect supporting a too large range of pandas versions, as an optional dependency, might require more work, so it would be good to re-evaluate minimal supported version.

At most, I think, it should have around the same support window as scipy (currently at 0.19 released March 2017) or matplotlib (currently at 2.1.0 released October 2017) => this would mean pandas 0.20.3 or 0.21.1.

This minimal supported pandas version (once we agree on it) should be added to CI.

I'm not sure if there are significant changes in pandas around 2017 - 2018 that would matter for our usage.
cc @jorisvandenbossche