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accepts ISO 8601-ish `+YYYYY` or `-YYYYY` notations. this is needed for the bijectivity of `to_string` and an upcoming `from_str`. |
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README.md |
README.md
Chrono 0.2.0-dev
Date and time handling for Rust. (also known as rust-chrono
)
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 builts upon and should acknowledge:
- Initial research on the wiki
- Dietrich Epp's datetime-rs
- Luis de Bethencourt's rust-datetime
Usage
Put this in your Cargo.toml
:
[dependencies]
chrono = "0.2"
And this in your crate root:
extern crate chrono;
Overview
Duration
Chrono used to have a Duration
type, which represents the time span.
Now Rust standard library includes it as std::time::duration::Duration
and
Chrono simply reexports it.
Date and Time
Chrono provides a DateTime
type for the combined date and time.
DateTime
, among others, is timezone-aware and
must be constructed from the timezone object (Offset
).
DateTime
s with different offsets do not mix, but can be converted to each other.
You can get the current date and time in the UTC timezone (UTC::now()
)
or in the local timezone (Local::now()
).
use chrono::{UTC, Local, DateTime};
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::{UTC, Offset, Weekday, 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);
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::{UTC, Local, Datelike, Timelike, Weekday, Duration};
// assume this returned `2014-11-28T21:45:59.324310806+09:00`:
let dt = Local::now();
// 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, ..., Sat=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
// offset accessor and manipulation
assert_eq!(dt.offset().local_minus_utc(), Duration::hours(9));
assert_eq!(dt.with_offset(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
assert_eq!(UTC.ymd(2014, 11, 14).and_hms(8, 9, 10) - UTC.ymd(2014, 11, 14).and_hms(10, 9, 8),
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 the format::strftime
module documentation for full syntax.)
The default to_string
method and {:?}
specifier also give a reasonable representation.
use chrono::{UTC, Offset};
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("%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!(format!("{:?}", dt), "2014-11-28T12:00:09Z");
Parsing can be done with two methods:
-
DateTime::parse_from_str
parses 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. -
Offset::datetime_from_str
is similar but returnsDateTime
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::{UTC, Offset, DateTime};
let dt = UTC.ymd(2014, 11, 28).and_hms(12, 0, 9);
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_eq!(DateTime::parse_from_str("2014-11-28 21:00:09 +09:00",
"%Y-%m-%d %H:%M:%S %z").map(|dt| dt.with_offset(UTC)), Ok(dt));
// 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());
Individual date and time
Chrono also provides an individual date type (Date
) and time type (Time
).
They also have offsets attached, and have to be constructed via offsets.
Most operations available to DateTime
are also available to Date
and Time
whenever appropriate.
use chrono::{UTC, Local, Offset, LocalResult, Datelike, Weekday};
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.hms_milli(7, 8, 9, 10).format("%H%M%S").to_string(), "070809");
DateTime
has two methods, date
and time
,
which return narrow views to its date and time components respectively.
Naive date and time
Chrono provides naive counterparts to Date
, Time
and DateTime
as NaiveDate
, NaiveTime
and NaiveDateTime
respectively.
They have almost equivalent interfaces as their timezone-aware twins, but are not associated to offsets obviously and can be quite low-level. They are mostly useful for building blocks for higher-level types.
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
.
Advanced offset handling is not yet supported (but is planned in 0.3).