Expand description
Chrono: Date and Time for Rust
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:
- Initial research on the wiki
- Dietrich Epp’s datetime-rs
- Luis de Bethencourt’s rust-datetime
Any significant changes to Chrono are documented in
the CHANGELOG.md file.
Usage
Put this in your Cargo.toml:
[dependencies]
chrono = "0.4"Features
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 ofallocand adds interoperation with standard library types and traits.clock: Enables reading the system time (now) that depends on the standard library for UNIX-like operating systems and the Windows API (winapi) for Windows.
Optional features:
serde: Enable serialization/deserialization via serde.unstable-locales: Enable localization. This adds various methods with a_localizedsuffix. 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.
Overview
Duration
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.
Date and Time
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:
-
Utcspecifies the UTC time zone. It is most efficient. -
Localspecifies the system local time zone. -
FixedOffsetspecifies 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 otherTimeZones 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(); // e.g. `2014-11-28T12:45:59.324310806Z`
let local: DateTime<Local> = Local::now(); // e.g. `2014-11-28T21:45:59.324310806+09:00`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); // `2014-07-08T09:10:11Z`
// July 8 is 188th day of the year 2014 (`o` for "ordinal")
assert_eq!(dt, Utc.yo(2014, 189).and_hms(9, 10, 11));
// July 8 is Tuesday in ISO week 28 of the year 2014.
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); // `2014-07-08T09:10:11.012Z`
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));
// dynamic verification
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);
// other time zone objects can be used to construct a local datetime.
// obviously, `local_dt` is normally different from `dt`, but `fixed_dt` should be identical.
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;
// assume this returned `2014-11-28T21:45:59.324310806+09:00`:
let dt = FixedOffset::east(9*3600).ymd(2014, 11, 28).and_hms_nano(21, 45, 59, 324310806);
// property accessors
assert_eq!((dt.year(), dt.month(), dt.day()), (2014, 11, 28));
assert_eq!((dt.month0(), dt.day0()), (10, 27)); // for unfortunate souls
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); // Mon=1, ..., Sun=7
assert_eq!(dt.ordinal(), 332); // the day of year
assert_eq!(dt.num_days_from_ce(), 735565); // the number of days from and including Jan 1, 1
// time zone accessor and manipulation
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));
// a sample of property manipulations (validates dynamically)
assert_eq!(dt.with_day(29).unwrap().weekday(), Weekday::Sat); // 2014-11-29 is Saturday
assert_eq!(dt.with_day(32), None);
assert_eq!(dt.with_year(-300).unwrap().num_days_from_ce(), -109606); // November 29, 301 BCE
// arithmetic operations
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 and Parsing
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");
// Note that milli/nanoseconds are only printed if they are non-zero
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
FromStrtrait (andparsemethod on a string) can be used for parsingDateTime<FixedOffset>,DateTime<Utc>andDateTime<Local>values. This parses what the{:?}(std::fmt::Debug) format specifier prints, and requires the offset to be present. -
DateTime::parse_from_strparses a date and time with offsets and returnsDateTime<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_rfc2822andDateTime::parse_from_rfc3339are similar but for well-known formats. -
Offset::datetime_from_stris similar but returnsDateTimeof 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));
// method 1
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()));
// method 2
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()));
// method 3
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()));
// oops, the year is missing!
assert!(Utc.datetime_from_str("Fri Nov 28 12:00:09", "%a %b %e %T %Y").is_err());
// oops, the format string does not include the year at all!
assert!(Utc.datetime_from_str("Fri Nov 28 12:00:09", "%a %b %e %T").is_err());
// oops, the weekday is incorrect!
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.
Conversion from and to EPOCH timestamps
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.
// We need the trait in scope to use Utc::timestamp().
use chrono::{DateTime, TimeZone, Utc};
// Construct a datetime from epoch:
let dt = Utc.timestamp(1_500_000_000, 0);
assert_eq!(dt.to_rfc2822(), "Fri, 14 Jul 2017 02:40:00 +0000");
// Get epoch value from a datetime:
let dt = DateTime::parse_from_rfc2822("Fri, 14 Jul 2017 02:40:00 +0000").unwrap();
assert_eq!(dt.timestamp(), 1_500_000_000);Individual date
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.
Naive date and time
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.
Limitations
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.
Re-exports
pub use format::ParseError;pub use format::ParseResult;pub use naive::IsoWeek;pub use naive::NaiveDate;pub use naive::NaiveDateTime;pub use naive::NaiveTime;pub use naive::NaiveWeek;pub use offset::Local;pub use offset::FixedOffset;pub use offset::LocalResult;pub use offset::Offset;pub use offset::TimeZone;pub use offset::Utc;Modules
use chrono::prelude::*;).Structs
<Month> value with FromStr.Weekday value with FromStr.Enums
DurationConstants
Date.DateTime<Utc>.Date.DateTime<Utc>.