Why does icu_time::ZonedDateTime not implement serde::Serialize?

[LeandroVandari]

In developing an application, one of my requirements is to be able to store ZonedDateTimes to files, so I can know when given things happened.

I figured I could simply serialize the containing struct with serde, but found out ZonedDateTime doesn't implement serde::Serialize. What I find most weird about this, is that ZoneNameTimestamp does implement serde::Serialize, and it does it (basically) through a manual implementation of serialize for ZonedDateTime. So, my question is, why doesn't ZonedDateTime implement serde::Serialize (and Deserialize)?

Note: I'd be happy to make a PR for such an implementation, but thought it best to ask here before doing it, because I've made wrong assumptions about unimplemented traits in this crate before :p

[sffc]

Hi, thanks for the question! Could you clarify your use-case?

The datetime types in icu do not implement many of the common helper traits, like Serialize or Ord, because they are not designed for storage or interchange. They are designed for formatting input and calendrical calculations.

We have worked closely with the authors of temporal_rs which ships a much more fully featured ZonedDateTime, including functions like to_ixdtf_string for serialization. You might also consider libraries such as time, jiff, and chrono.

[LeandroVandari]

I'm working on an app to create timelines of events, and I wanted

• high accuracy (ideally seconds+)
• a big range of years for my timestamps
• support for multiple calendar systems/formats (ideally being able to introduce my own)

After a bit of search, I stumbled upon icu, which seemed to support all of those. Right now I wanted to be able to store timelines to disk -- hence the need for Serialize. I understand how it might go beyond the scope of the type though, but I didn't find anything else (in icu_time) that could support the high accuracy+range of ZonedDateTime.

I had looked into temporal_rs at the start of my project, but somehow didn't find their ZonedDateTime. I'll definitely look into it, thanks for the recommendation! However, after skimming through it, it seems their version of the struct only supports the hardcoded calendars offered by icu_calendar, do you know how I could get around that? I'll take a look at the other mentioned crates as well... Thanks for the help!

[nekevss]

Hi, I'm one of the maintainers that work on temporal_rs. We do only support calendars that are supported by icu_calendar. There's not support for custom calendar systems as they were removed from the Temporal specification. There was also a decent burden involved in supporting custom calendars in the API. temporal_rs is also currently missing locale specific formatting.

In general though, if you decide to use temporal_rs and have any questions or run into issues, feel free to file an issue or reach out on Matrix! Would definitely be interested in feedback on the Rust API.

[LeandroVandari]

Thanks for your answer!

Custom calendars are currently not such a big issue for me (definitely not worth making my own calendar system haha), so I think I'll stick with temporal. Will definitely reach out if i stumble upon problems!