More human friendly timestamp specifications and/or ISO8601 compatibility ? (low priority)

It's more nice-to-have than anything, but I've been spoiled with systemd's time and date specifications.

Being able to do journalctl -u [someservice] --since "5h ago" is really nice!

I'd love to be able to do himalaya envelope list since "2 days ago"

Supporting such time specifications would be a great hassle, but a good first step might be to add ISO8601 compatibility with https://docs.rs/chrono/ or https://docs.rs/iso8601/.

If such timestamps were supported, one could do

himalaya envelope list after $(date --date="5 hours ago" --iso-8601=seconds)

and call it a day.