I really likes this package. And I may use it immediately. Very complete and detailed documentation. It lacks in some conveniences like iso8601, rfc3339 or other presets for formatting. But those can be handled manually. Thanks for this!
You should absolutely not need to handle ISO 8601 and RFC 3339 manually. They are supported via the Display and FromStr trait implementations on every main type in Jiff (Span, Zoned, Timestamp, civil::DateTime, civil::Date and civil::Time). It's technically an implementation of a mixture of ISO 8601, RFC 3339 and RFC 9557, but the grammar is specified precisely by Temporal. See: https://docs.rs/jiff/latest/jiff/fmt/temporal/index.html
Speaking of convenient things best not handled manually, do you have any plans to get support for it into crates like sqlx-postgresql, diesel or humantime where conversions need to happen but pretty much the same way for every user of the library?
Yeah this is a tough one. I'm not sure the right thing to do is for me to go around blasting PRs at those projects. They're probably already carrying support for both chrono and time, and asking them to support a third that is brand new is a bit of a stretch I think. Especially since I've promised breaking changes in the not-too-distant future. (Although I would like to do a Jiff 1.0 release about 1 year from now and commit to stability.) At least, I know I'd be hesitant if I were on the other side of it. But maybe folks are more flexible than me, I'm not sure.
I've been noodling on just adding these integrations to jiff itself. I do worry that if I do that, then the integrations will always stay with Jiff, even at 1.0. But maybe there just isn't another feasible choice.
But, why do you mention humantime? humantime doesn't have any integrations with time or chrono. humantime is more like a thin wrapper on top of std::time::Duration and std::time::SystemTime to make parsing and printing a bit nicer.