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,
There were several previous attempts to bring a good date and time library to Rust, which Chrono builts upon and should acknowledge:
Put this in your Cargo.toml:
toml
[dependencies]
chrono = "0.2"
And this in your crate root:
rust
extern crate chrono;
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.
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.
DateTimes with different time zones do not mix, but can be converted to each other.
You can get the current date and time in the UTC time zone (UTC::now())
or in the local time zone (Local::now()).
~~~~ {.rust} use chrono::*;
let utc: DateTime2014-11-28T12:45:59.324310806Z
let local: DateTime2014-11-28T21:45:59.324310806+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.
~~~~ {.rust} use chrono::*;
let dt = UTC.ymd(2014, 7, 8).andhms(9, 10, 11); // 2014-07-08T09:10:11Z
// July 8 is 188th day of the year 2014 (o for "ordinal")
asserteq!(dt, UTC.yo(2014, 189).andhms(9, 10, 11));
// July 8 is Tuesday in ISO week 28 of the year 2014.
asserteq!(dt, UTC.isoywd(2014, 28, Weekday::Tue).and_hms(9, 10, 11));
let dt = UTC.ymd(2014, 7, 8).andhmsmilli(9, 10, 11, 12); // 2014-07-08T09:10:11.012Z
asserteq!(dt, UTC.ymd(2014, 7, 8).andhmsmicro(9, 10, 11, 12000));
asserteq!(dt, UTC.ymd(2014, 7, 8).andhmsnano(9, 10, 11, 12000_000));
// dynamic verification asserteq!(UTC.ymdopt(2014, 7, 8).andhmsopt(21, 15, 33), LocalResult::Single(UTC.ymd(2014, 7, 8).andhms(21, 15, 33))); asserteq!(UTC.ymdopt(2014, 7, 8).andhmsopt(80, 15, 33), LocalResult::None); asserteq!(UTC.ymdopt(2014, 7, 38).andhms_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 localdt = Local.ymd(2014, 7, 8).andhmsmilli(9, 10, 11, 12);
let fixeddt = FixedOffset::east(9 * 3600).ymd(2014, 7, 8).andhmsmilli(18, 10, 11, 12);
asserteq!(dt, fixeddt);
~~~~
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:
~~~~ {.rust} use chrono::*;
// assume this returned 2014-11-28T21:45:59.324310806+09:00:
let dt = Local::now();
// property accessors asserteq!((dt.year(), dt.month(), dt.day()), (2014, 11, 28)); asserteq!((dt.month0(), dt.day0()), (10, 27)); // for unfortunate souls asserteq!((dt.hour(), dt.minute(), dt.second()), (21, 45, 59)); asserteq!(dt.weekday(), Weekday::Fri); asserteq!(dt.weekday().numberfrommonday(), 5); // Mon=1, ..., Sat=7 asserteq!(dt.ordinal(), 332); // the day of year asserteq!(dt.numdaysfromce(), 735565); // the number of days from and including Jan 1, 1
// time zone accessor and manipulation asserteq!(dt.offset().localminusutc(), Duration::hours(9)); asserteq!(dt.timezone(), FixedOffset::east(9 * 3600)); asserteq!(dt.withtimezone(&UTC), UTC.ymd(2014, 11, 28).andhmsnano(12, 45, 59, 324310806));
// a sample of property manipulations (validates dynamically) asserteq!(dt.withday(29).unwrap().weekday(), Weekday::Sat); // 2014-11-29 is Saturday asserteq!(dt.withday(32), None); asserteq!(dt.withyear(-300).unwrap().numdaysfrom_ce(), -109606); // November 29, 301 BCE
// arithmetic operations asserteq!(UTC.ymd(2014, 11, 14).andhms(8, 9, 10) - UTC.ymd(2014, 11, 14).andhms(10, 9, 8), Duration::seconds(-2 * 3600 + 2)); asserteq!(UTC.ymd(1970, 1, 1).andhms(0, 0, 0) + Duration::seconds(1000000000), UTC.ymd(2001, 9, 9).andhms(1, 46, 40)); asserteq!(UTC.ymd(1970, 1, 1).andhms(0, 0, 0) - Duration::seconds(1000000000), 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.
Chrono also provides to_rfc{2822,3339} methods for well-known formats.
~~~~ {.rust} use chrono::*;
let dt = UTC.ymd(2014, 11, 28).andhms(12, 0, 9); asserteq!(dt.format("%Y-%m-%d %H:%M:%S").tostring(), "2014-11-28 12:00:09"); asserteq!(dt.format("%a %b %e %T %Y").tostring(), "Fri Nov 28 12:00:09 2014"); asserteq!(dt.format("%a %b %e %T %Y").tostring(), dt.format("%c").tostring());
asserteq!(dt.tostring(), "2014-11-28 12:00:09 UTC"); asserteq!(dt.torfc2822(), "Fri, 28 Nov 2014 12:00:09 +0000"); asserteq!(dt.torfc3339(), "2014-11-28T12:00:09+00:00"); assert_eq!(format!("{:?}", dt), "2014-11-28T12:00:09Z"); ~~~~
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_rfc{2822,3339} 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.
~~~~ {.rust} use chrono::*;
let dt = UTC.ymd(2014, 11, 28).andhms(12, 0, 9); let fixeddt = dt.with_timezone(&FixedOffset::east(9*3600));
// method 1
asserteq!("2014-11-28T12:00:09Z".parse::
// method 2 asserteq!(DateTime::parsefromstr("2014-11-28 21:00:09 +09:00", "%Y-%m-%d %H:%M:%S %z"), Ok(fixeddt.clone())); asserteq!(DateTime::parsefromrfc2822("Fri, 28 Nov 2014 21:00:09 +0900"), Ok(fixeddt.clone())); asserteq!(DateTime::parsefromrfc3339("2014-11-28T21:00:09+09:00"), Ok(fixeddt.clone()));
// method 3 asserteq!(UTC.datetimefromstr("2014-11-28 12:00:09", "%Y-%m-%d %H:%M:%S"), Ok(dt.clone())); asserteq!(UTC.datetimefromstr("Fri Nov 28 12:00:09 2014", "%a %b %e %T %Y"), Ok(dt.clone()));
// oops, the year is missing! assert!(UTC.datetimefromstr("Fri Nov 28 12:00:09", "%a %b %e %T %Y").iserr()); // oops, the format string does not include the year at all! assert!(UTC.datetimefromstr("Fri Nov 28 12:00:09", "%a %b %e %T").iserr()); // oops, the weekday is incorrect! assert!(UTC.datetimefromstr("Sat Nov 28 12:00:09 2014", "%a %b %e %T %Y").is_err()); ~~~~
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.
~~~~ {.rust} use chrono::*;
asserteq!(UTC::today(), UTC::now().date()); asserteq!(Local::today(), Local::now().date());
asserteq!(UTC.ymd(2014, 11, 28).weekday(), Weekday::Fri); asserteq!(UTC.ymdopt(2014, 11, 31), LocalResult::None); asserteq!(UTC.ymd(2014, 11, 28).andhmsmilli(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.
Advanced time zone handling is not yet supported (but is planned in 0.3).