ENH: support datetime64, datetime64tz in nanops.mean, nanops.median
Tracking down relevant issues and figuring out test coverage is the "WIP" part of this.
this looks good. can you add a deprecation note in whatsnew and rebase. whatsnew added, rebased+green lgtm. once more rebase and merge on green. (also add to the deprecated issue tracker as well). Thanks @jbrockmendel 