Converting a timestamp to local time is verbose and unintuitive

[johnomalley]

My (simplified) use case - build a vector of file metadata (name + modified timestamp), then sort by most recent and output a name + formatted timestamp for each one in local time. This is a trivial problem in Java, C#, JavaScript, etc. As far as I can tell this is what I need to do in chrono:

fn format_time(modified: i64) -> String {
    DateTime::<Utc>::from_utc(NaiveDateTime::from_timestamp(modified, 0), Utc).with_timezone(&Local).format("%Y-%m-%d %H:%M:%S").to_string()
}

This took me a few hours to figure out. Wow! I thought Java APIs were verbose. Maybe there's an easier way but it's not obvious from the docs.

The docs refer to Local.from_timestamp(...) but that does not compile (apologies if I'm missing something as I'm new to Rust).

[quodlibetor]

It is sadly the case that our from_* methods are poorly named and don't include from_* at all. The are all implemented on the TimeZone trait which is part of the chrono prelude.

But for example this works:

extern crate chrono;

use chrono::prelude::*;

fn main() {
    println!("{}", Local.timestamp(90, 0));
}

and outputs: 1970-01-01 00:01:30 +00:00.

In fact, the only places in the chrono docs that I can find that use the extremely verbose construction that you used (on DateTime) immediately gives the equivalent shorter constructor.

I'm going to add an issue to create from_* methods (and deprecate the existing constructors) on timezone, because the current situation is extremely confusing.

[johnomalley]

Ah much better - thanks for your reply. Closing.