%Z can't print the timezone abbreviation

[howjmay]

Hi I am having a use case that I need to generate formatted time, and the text should contain the abbreviation of the timezone.
I am using format_with_items(), and a format string "%a %b %d %I:%M:%S '%Z' %p %Y". However, %Z doesn't return the abbreviation. What should I do?

[djc]

This issue doesn't come with a reproducible example, nor does it show the actual output. Please extend your bug report.

[howjmay]

@djc An example is like following

use chrono::{format::StrftimeItems, Local};

fn main() {
    let now = Local::now();
    now.with_timezone(now.offset());
    let formatted = now
        .format_with_items(StrftimeItems::new("%a %b %d %I:%M:%S '%Z' %Y"))
        .to_string();
    println!("{formatted}");
}

expected result

Tue Feb 14 00:55:01 'CET' 2023

actual result

Tue Feb 14 12:56:24 '+08:00' 2023

The expected abbreviation CET is replaced by +08:00. Or I should use other escape character then I can get the abbreviation of timezone?

[djc]

chrono itself doesn't know timezones beyond their offsets, so I don't think it can do what you want. Maybe look at the chrono-tz crate and see if it can help with this?

[esheppa]

@howjmay - please see also this issue: #749.

chrono-tz should do this correctly as per here as the display implementation of the TimeZone type is called. You can use chrono-tz and iana-time-zone (a dependency of chrono) together to have behaviour equivalent to local. First use iana-time-zone to get the name of the locally set timezone, then you can parse that into a chrono_tz::Tz, as per the example:

let tz_str = iana_time_zone::get_timezone()?;
let tz: chrono_tz::Tz = tz_str.parse()?;

There is also a partially complete PR to solve this #750 and we would appreciate any thoughts or comments you have on it.

[howjmay]

Hi @esheppa the method you provided is good.
However, I found a problem when I checkout the list in chono_tz. The abbreviations of the timezones in chrono_tz seems not complete.
See the wiki https://en.wikipedia.org/wiki/List_of_time_zone_abbreviations
Most of the abbreviation doesn't exist in the list in chono_tz. Or I misunderstand the way to use it?

[djc]

chrono-tz includes data from the IANA database. It's definitely possible that this doesn't encompass all abbreviations listed on Wikipedia. I think it is reasonable to consider the IANA database authoritative in this regard.

[howjmay]

thanks!

[campbellcole]

While this being an issue is understandable, the documentation makes it seem like chrono should be able to do this:

https://docs.rs/chrono/latest/chrono/format/strftime/index.html

There are even footnotes for this specifier but none that say it isn't supported for formatting. If possible, I would love the documentation to reflect this. Thanks for your time.

[pitdicker]

@campbellcole Would you be willing to make a PR?

[campbellcole]

Sure! Will do that tomorrow evening if that’s alright with you.

…

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[campbellcole]

For anyone finding this issue from the documentation, you can accomplish this using two additional crates (chrono-tz and iana-time-zone):

use chrono::{TimeZone, Utc};
use chrono_tz::{OffsetName, Tz};
use iana_time_zone::get_timezone;

let tz_str = get_timezone().unwrap();
let tz: Tz = tz_str.parse().unwrap();
let offset = tz.offset_from_utc_date(&Utc::now().date_naive());
let abbreviation = offset.abbreviation();
println!("{abbreviation}");

[djc]

Better documented in #1051.