-
It aims to be a feature-complete superset of
-the time library.
-In particular,
-
-- Chrono strictly adheres to ISO 8601.
-- Chrono is timezone-aware by default, with separate timezone-naive types.
-- Chrono is space-optimal and (while not being the primary goal) reasonably efficient.
-
-
There were several previous attempts to bring a good date and time library to Rust,
-which Chrono builds upon and should acknowledge:
-
-
Any significant changes to Chrono are documented in
-the CHANGELOG.md file.
-
-
Put this in your Cargo.toml:
-
[dependencies]
-chrono = "0.4"
-
-
-
Chrono supports various runtime environments and operating systems, and has
-several features that may be enabled or disabled.
-
Default features:
-
-alloc: Enable features that depend on allocation (primarily string formatting)
-std: Enables functionality that depends on the standard library. This
-is a superset of alloc and adds interoperation with standard library types
-and traits.
-clock: enables reading the system time (now), independent of whether
-std::time::SystemTime is present, depends on having a libc.
-
-
Optional features:
-
-wasmbind: Enable integration with wasm-bindgen and its js-sys project
-serde: Enable serialization/deserialization via serde.
-unstable-locales: Enable localization. This adds various methods with a
-_localized suffix. The implementation and API may change or even be
-removed in a patch release. Feedback welcome.
-
-
See the cargo docs for examples of specifying features.
-
-
Chrono currently uses its own Duration type to represent the magnitude
-of a time span. Since this has the same name as the newer, standard type for
-duration, the reference will refer this type as OldDuration.
-
Note that this is an "accurate" duration represented as seconds and
-nanoseconds and does not represent "nominal" components such as days or
-months.
-
When the oldtime feature is enabled, Duration is an alias for the
-time::Duration
-type from v0.1 of the time crate. time v0.1 is deprecated, so new code
-should disable the oldtime feature and use the chrono::Duration type
-instead. The oldtime feature is enabled by default for backwards
-compatibility, but future versions of Chrono are likely to remove the
-feature entirely.
-
Chrono does not yet natively support
-the standard Duration type,
-but it will be supported in the future.
-Meanwhile you can convert between two types with
-Duration::from_std
-and
-Duration::to_std
-methods.
-
-
Chrono provides a
-DateTime
-type to represent a date and a time in a timezone.
-
For more abstract moment-in-time tracking such as internal timekeeping
-that is unconcerned with timezones, consider
-time::SystemTime,
-which tracks your system clock, or
-time::Instant, which
-is an opaque but monotonically-increasing representation of a moment in time.
-
DateTime is timezone-aware and must be constructed from
-the TimeZone object,
-which defines how the local date is converted to and back from the UTC date.
-There are three well-known TimeZone implementations:
-
--
-
Utc specifies the UTC time zone. It is most efficient.
-
--
-
Local specifies the system local time zone.
-
--
-
FixedOffset specifies
-an arbitrary, fixed time zone such as UTC+09:00 or UTC-10:30.
-This often results from the parsed textual date and time.
-Since it stores the most information and does not depend on the system environment,
-you would want to normalize other TimeZones into this type.
-
-
-
DateTimes with different TimeZone types are distinct and do not mix,
-but can be converted to each other using
-the DateTime::with_timezone method.
-
You can get the current date and time in the UTC time zone
-(Utc::now())
-or in the local time zone
-(Local::now()).
-
-
-use chrono::prelude::*;
-
-let utc: DateTime<Utc> = Utc::now();
-let local: DateTime<Local> = Local::now();
-
Alternatively, you can create your own date and time.
-This is a bit verbose due to Rust's lack of function and method overloading,
-but in turn we get a rich combination of initialization methods.
-
-
-use chrono::prelude::*;
-use chrono::offset::LocalResult;
-
-let dt = Utc.ymd(2014, 7, 8).and_hms(9, 10, 11);
-
-assert_eq!(dt, Utc.yo(2014, 189).and_hms(9, 10, 11));
-
-assert_eq!(dt, Utc.isoywd(2014, 28, Weekday::Tue).and_hms(9, 10, 11));
-
-let dt = Utc.ymd(2014, 7, 8).and_hms_milli(9, 10, 11, 12);
-assert_eq!(dt, Utc.ymd(2014, 7, 8).and_hms_micro(9, 10, 11, 12_000));
-assert_eq!(dt, Utc.ymd(2014, 7, 8).and_hms_nano(9, 10, 11, 12_000_000));
-
-
-assert_eq!(Utc.ymd_opt(2014, 7, 8).and_hms_opt(21, 15, 33),
- LocalResult::Single(Utc.ymd(2014, 7, 8).and_hms(21, 15, 33)));
-assert_eq!(Utc.ymd_opt(2014, 7, 8).and_hms_opt(80, 15, 33), LocalResult::None);
-assert_eq!(Utc.ymd_opt(2014, 7, 38).and_hms_opt(21, 15, 33), LocalResult::None);
-
-
-
-let local_dt = Local.ymd(2014, 7, 8).and_hms_milli(9, 10, 11, 12);
-let fixed_dt = FixedOffset::east(9 * 3600).ymd(2014, 7, 8).and_hms_milli(18, 10, 11, 12);
-assert_eq!(dt, fixed_dt);
-
Various properties are available to the date and time, and can be altered individually.
-Most of them are defined in the traits Datelike and
-Timelike which you should use before.
-Addition and subtraction is also supported.
-The following illustrates most supported operations to the date and time:
-
-
-
-use chrono::prelude::*;
-use chrono::Duration;
-
-
-let dt = FixedOffset::east(9*3600).ymd(2014, 11, 28).and_hms_nano(21, 45, 59, 324310806);
-
-
-assert_eq!((dt.year(), dt.month(), dt.day()), (2014, 11, 28));
-assert_eq!((dt.month0(), dt.day0()), (10, 27));
-assert_eq!((dt.hour(), dt.minute(), dt.second()), (21, 45, 59));
-assert_eq!(dt.weekday(), Weekday::Fri);
-assert_eq!(dt.weekday().number_from_monday(), 5);
-assert_eq!(dt.ordinal(), 332);
-assert_eq!(dt.num_days_from_ce(), 735565);
-
-
-assert_eq!(dt.offset().fix().local_minus_utc(), 9 * 3600);
-assert_eq!(dt.timezone(), FixedOffset::east(9 * 3600));
-assert_eq!(dt.with_timezone(&Utc), Utc.ymd(2014, 11, 28).and_hms_nano(12, 45, 59, 324310806));
-
-
-assert_eq!(dt.with_day(29).unwrap().weekday(), Weekday::Sat);
-assert_eq!(dt.with_day(32), None);
-assert_eq!(dt.with_year(-300).unwrap().num_days_from_ce(), -109606);
-
-
-let dt1 = Utc.ymd(2014, 11, 14).and_hms(8, 9, 10);
-let dt2 = Utc.ymd(2014, 11, 14).and_hms(10, 9, 8);
-assert_eq!(dt1.signed_duration_since(dt2), Duration::seconds(-2 * 3600 + 2));
-assert_eq!(dt2.signed_duration_since(dt1), Duration::seconds(2 * 3600 - 2));
-assert_eq!(Utc.ymd(1970, 1, 1).and_hms(0, 0, 0) + Duration::seconds(1_000_000_000),
- Utc.ymd(2001, 9, 9).and_hms(1, 46, 40));
-assert_eq!(Utc.ymd(1970, 1, 1).and_hms(0, 0, 0) - Duration::seconds(1_000_000_000),
- Utc.ymd(1938, 4, 24).and_hms(22, 13, 20));
-
-
Formatting is done via the format method,
-which format is equivalent to the familiar strftime format.
-
See format::strftime
-documentation for full syntax and list of specifiers.
-
The default to_string method and {:?} specifier also give a reasonable representation.
-Chrono also provides to_rfc2822 and
-to_rfc3339 methods
-for well-known formats.
-
Chrono now also provides date formatting in almost any language without the
-help of an additional C library. This functionality is under the feature
-unstable-locales:
-
chrono { version = "0.4", features = ["unstable-locales"]
-
-
The unstable-locales feature requires and implies at least the alloc feature.
-
-
-use chrono::prelude::*;
-
-let dt = Utc.ymd(2014, 11, 28).and_hms(12, 0, 9);
-assert_eq!(dt.format("%Y-%m-%d %H:%M:%S").to_string(), "2014-11-28 12:00:09");
-assert_eq!(dt.format("%a %b %e %T %Y").to_string(), "Fri Nov 28 12:00:09 2014");
-assert_eq!(dt.format_localized("%A %e %B %Y, %T", Locale::fr_BE).to_string(), "vendredi 28 novembre 2014, 12:00:09");
-assert_eq!(dt.format("%a %b %e %T %Y").to_string(), dt.format("%c").to_string());
-
-assert_eq!(dt.to_string(), "2014-11-28 12:00:09 UTC");
-assert_eq!(dt.to_rfc2822(), "Fri, 28 Nov 2014 12:00:09 +0000");
-assert_eq!(dt.to_rfc3339(), "2014-11-28T12:00:09+00:00");
-assert_eq!(format!("{:?}", dt), "2014-11-28T12:00:09Z");
-
-
-let dt_nano = Utc.ymd(2014, 11, 28).and_hms_nano(12, 0, 9, 1);
-assert_eq!(format!("{:?}", dt_nano), "2014-11-28T12:00:09.000000001Z");
-
Parsing can be done with three methods:
-
--
-
The standard FromStr trait
-(and parse method
-on a string) can be used for parsing DateTime<FixedOffset>, DateTime<Utc> and
-DateTime<Local> values. This parses what the {:?}
-(std::fmt::Debug)
-format specifier prints, and requires the offset to be present.
-
--
-
DateTime::parse_from_str parses
-a date and time with offsets and returns DateTime<FixedOffset>.
-This should be used when the offset is a part of input and the caller cannot guess that.
-It cannot be used when the offset can be missing.
-DateTime::parse_from_rfc2822
-and
-DateTime::parse_from_rfc3339
-are similar but for well-known formats.
-
--
-
Offset::datetime_from_str is
-similar but returns DateTime of given offset.
-When the explicit offset is missing from the input, it simply uses given offset.
-It issues an error when the input contains an explicit offset different
-from the current offset.
-
-
-
More detailed control over the parsing process is available via
-format module.
-
-
-use chrono::prelude::*;
-
-let dt = Utc.ymd(2014, 11, 28).and_hms(12, 0, 9);
-let fixed_dt = dt.with_timezone(&FixedOffset::east(9*3600));
-
-
-assert_eq!("2014-11-28T12:00:09Z".parse::<DateTime<Utc>>(), Ok(dt.clone()));
-assert_eq!("2014-11-28T21:00:09+09:00".parse::<DateTime<Utc>>(), Ok(dt.clone()));
-assert_eq!("2014-11-28T21:00:09+09:00".parse::<DateTime<FixedOffset>>(), Ok(fixed_dt.clone()));
-
-
-assert_eq!(DateTime::parse_from_str("2014-11-28 21:00:09 +09:00", "%Y-%m-%d %H:%M:%S %z"),
- Ok(fixed_dt.clone()));
-assert_eq!(DateTime::parse_from_rfc2822("Fri, 28 Nov 2014 21:00:09 +0900"),
- Ok(fixed_dt.clone()));
-assert_eq!(DateTime::parse_from_rfc3339("2014-11-28T21:00:09+09:00"), Ok(fixed_dt.clone()));
-
-
-assert_eq!(Utc.datetime_from_str("2014-11-28 12:00:09", "%Y-%m-%d %H:%M:%S"), Ok(dt.clone()));
-assert_eq!(Utc.datetime_from_str("Fri Nov 28 12:00:09 2014", "%a %b %e %T %Y"), Ok(dt.clone()));
-
-
-assert!(Utc.datetime_from_str("Fri Nov 28 12:00:09", "%a %b %e %T %Y").is_err());
-
-assert!(Utc.datetime_from_str("Fri Nov 28 12:00:09", "%a %b %e %T").is_err());
-
-assert!(Utc.datetime_from_str("Sat Nov 28 12:00:09 2014", "%a %b %e %T %Y").is_err());
-
Again : See format::strftime
-documentation for full syntax and list of specifiers.
-
-
Use Utc.timestamp(seconds, nanoseconds)
-to construct a DateTime<Utc> from a UNIX timestamp
-(seconds, nanoseconds that passed since January 1st 1970).
-
Use DateTime.timestamp to get the timestamp (in seconds)
-from a DateTime. Additionally, you can use
-DateTime.timestamp_subsec_nanos
-to get the number of additional number of nanoseconds.
-
-
-
-use chrono::{DateTime, TimeZone, Utc};
-
-
-let dt = Utc.timestamp(1_500_000_000, 0);
-assert_eq!(dt.to_rfc2822(), "Fri, 14 Jul 2017 02:40:00 +0000");
-
-
-let dt = DateTime::parse_from_rfc2822("Fri, 14 Jul 2017 02:40:00 +0000").unwrap();
-assert_eq!(dt.timestamp(), 1_500_000_000);
-
-
Chrono also provides an individual date type (Date).
-It also has time zones attached, and have to be constructed via time zones.
-Most operations available to DateTime are also available to Date whenever appropriate.
-
-
-use chrono::prelude::*;
-use chrono::offset::LocalResult;
-
-assert_eq!(Utc::today(), Utc::now().date());
-assert_eq!(Local::today(), Local::now().date());
-
-assert_eq!(Utc.ymd(2014, 11, 28).weekday(), Weekday::Fri);
-assert_eq!(Utc.ymd_opt(2014, 11, 31), LocalResult::None);
-assert_eq!(Utc.ymd(2014, 11, 28).and_hms_milli(7, 8, 9, 10).format("%H%M%S").to_string(),
- "070809");
-
There is no timezone-aware Time due to the lack of usefulness and also the complexity.
-
DateTime has date method
-which returns a Date which represents its date component.
-There is also a time method,
-which simply returns a naive local time described below.
-
-
Chrono provides naive counterparts to Date, (non-existent) Time and DateTime
-as NaiveDate,
-NaiveTime and
-NaiveDateTime respectively.
-
They have almost equivalent interfaces as their timezone-aware twins,
-but are not associated to time zones obviously and can be quite low-level.
-They are mostly useful for building blocks for higher-level types.
-
Timezone-aware DateTime and Date types have two methods returning naive versions:
-naive_local returns
-a view to the naive local time,
-and naive_utc returns
-a view to the naive UTC time.
-
-
Only proleptic Gregorian calendar (i.e. extended to support older dates) is supported.
-Be very careful if you really have to deal with pre-20C dates, they can be in Julian or others.
-
Date types are limited in about +/- 262,000 years from the common epoch.
-Time types are limited in the nanosecond accuracy.
-
Leap seconds are supported in the representation but
-Chrono doesn't try to make use of them.
-(The main reason is that leap seconds are not really predictable.)
-Almost every operation over the possible leap seconds will ignore them.
-Consider using NaiveDateTime with the implicit TAI (International Atomic Time) scale
-if you want.
-
Chrono inherently does not support an inaccurate or partial date and time representation.
-Any operation that can be ambiguous will return None in such cases.
-For example, "a month later" of 2014-01-30 is not well-defined
-and consequently Utc.ymd(2014, 1, 30).with_month(2) returns None.
-
Non ISO week handling is not yet supported.
-For now you can use the chrono_ext
-crate (sources).
-
Advanced time zone handling is not yet supported.
-For now you can try the Chrono-tz crate instead.
-
-