libtzfile

This library reads and parses the system timezone information files (TZ Files) provided by IANA.

The default feature is std. With default-features = false, the crate is no_std and uses alloc::vec. In both cases the new() method returns a Tz struct containing the TZfile fields as described in the man page (http://man7.org/linux/man-pages/man5/tzfile.5.html).

• with no_std the function signature is new(buf: Vec<u8>) where buf is the TZ File data

// no_std
[dependencies]
libtzfile = { version = "3.1.0", default-features = false }

let tzfile = include_bytes!("/usr/share/zoneinfo/America/Phoenix").to_vec();
let tz = Tz::new(tzfile).unwrap();

• with std which is the default feature the function signature is new(tz: &str) where tz is the TZ File name

// std is the default
[dependencies]
libtzfile = "3.1.0"

use libtzfile::Tz;
let tzfile: &str = "/usr/share/zoneinfo/America/Phoenix";
println!("{:?}", Tz::new(tzfile).unwrap());

Tz { tzh_timecnt_data: [-2717643600, -1633273200, -1615132800, -1601823600, -1583683200, -880210800, -820519140, -812653140, -796845540, -84380400, -68659200], tzh_timecnt_indices: [2, 1, 2, 1, 2, 3, 2, 3, 2, 1, 2], tzh_typecnt: [Ttinfo { tt_utoff: -26898, tt_isdst: 0, tt_abbrind: 0 }, Ttinfo { tt_utoff: -21600, tt_isdst: 1, tt_abbrind: 1 }, Ttinfo { tt_utoff: -25200, tt_isdst: 0, tt_abbrind: 2 }, Ttinfo { tt_utoff: -21600, tt_isdst: 1, tt_abbrind: 3 }], tz_abbr: ["LMT", "MDT", "MST", "MWT"] }

For higher level parsing, you can enable the parse or json features. For instance, to display 2020 DST transitions in France, you can use the transition_times method:

use libtzfile::Tz;
let tzfile: &str = "/usr/share/zoneinfo/Europe/Paris";
println!("{:?}", Tz::new(tzfile).unwrap().transition_times(Some(2020)).unwrap());

[TransitionTime { time: 2020-03-29T01:00:00Z, utc_offset: 7200, isdst: true, abbreviation: "CEST" }, TransitionTime { time: 2020-10-25T01:00:00Z, utc_offset: 3600, isdst: false, abbreviation: "CET" }]

If you want more complete information about the timezone, you can use the zoneinfo method, which returns a more complete structure:

use libtzfile::Tz;
let tzfile: &str = "/usr/share/zoneinfo/Europe/Paris";
println!("{:?}", Tz::new(tzfile).unwrap().zoneinfo().unwrap());

Tzinfo { timezone: "Europe/Paris", utc_datetime: 2020-09-05T16:41:44.279502100Z, datetime: 2020-09-05T18:41:44.279502100+02:00, dst_from: Some(2020-03-29T01:00:00Z), dst_until: Some(2020-10-25T01:00:00Z), dst_period: true, raw_offset: 3600, dst_offset: 7200, utc_offset: +02:00, abbreviation: "CEST", week_number: 36 }

This more complete structure implements the Serialize trait and can be transformed to a json string via a method of the json feature (which includes methods from the parse feature):

use libtzfile::{Tz, TzError};
let tzfile: &str = "/usr/share/zoneinfo/Europe/Paris";
let tz = Tz::new(tzfile)?
    .zoneinfo()?
    .to_json()?;
println!("{}", tz);

{"timezone":"Europe/Paris","utc_datetime":"2020-09-05T18:04:50.546668500Z","datetime":"2020-09-05T20:04:50.546668500+02:00","dst_from":"2020-03-29T01:00:00Z","dst_until":"2020-10-25T01:00:00Z","dst_period":true,"raw_offset":3600,"dst_offset":7200,"utc_offset":"+02:00","abbreviation":"CEST","week_number":36}

This feature is used in my world time API.

The tests (cargo test, cargo test --no-default-features or cargo test --features parse|json) are working with the 2024a timezone database.

License: MIT