Struct DateTimeFormatter

pub struct DateTimeFormatter(/* private fields */);

DateTimeFormatter is a formatter capable of formatting date/times from any calendar, selected at runtime. For the difference between this and TypedDateTimeFormatter, please read the crate root docs.

When constructed, it uses data from the data provider, selected locale and provided options to collect all data necessary to format any dates into that locale.

For that reason, one should think of the process of formatting a date in two steps - first, a computational heavy construction of DateTimeFormatter, and then fast formatting of DateTime data using the instance. 📏 This item has a stack size of 5208 bytes on the stable toolchain at release date.

Examples

use icu::calendar::DateTime;
use icu::datetime::{options::length, DateTimeFormatter};
use icu::locid::locale;
use writeable::assert_writeable_eq;

let mut options = length::Bag::from_date_time_style(
    length::Date::Medium,
    length::Time::Short,
);

let dtf = DateTimeFormatter::try_new(
    &locale!("en-u-ca-gregory").into(),
    options.into(),
)
.expect("Failed to create DateTimeFormatter instance.");

let datetime = DateTime::try_new_iso_datetime(2020, 9, 1, 12, 34, 28)
    .expect("Failed to construct DateTime.");
let any_datetime = datetime.to_any();

assert_writeable_eq!(
    dtf.format(&any_datetime).expect("Calendars should match"),
    "Sep 1, 2020, 12:34 PM"
);

Since this works with AnyCalendar, you can use DateTime with AnyCalendar to have a date in a runtime-selected calendar:

use icu::calendar::{AnyCalendar, DateTime, Time};
use icu::datetime::{options::length, DateTimeFormatter};
use icu::locid::locale;
use writeable::assert_writeable_eq;

let locale = locale!("en-u-ca-japanese").into(); // English with the Japanese calendar

let calendar = AnyCalendar::new_for_locale(&locale);
let calendar = Rc::new(calendar); // Avoid cloning it


// manually construct a datetime in this calendar
let manual_time = Time::try_new(12, 33, 12, 0).expect("failed to construct Time");
// construct from era code, year, month code, day, time, and a calendar
// This is March 28, 15 Heisei
let manual_datetime = DateTime::try_new_from_codes("heisei".parse().unwrap(), 15, "M03".parse().unwrap(), 28,
                                               manual_time, calendar.clone())
                    .expect("Failed to construct DateTime manually");


// construct another datetime by converting from ISO
let iso_datetime = DateTime::try_new_iso_datetime(2020, 9, 1, 12, 34, 28)
    .expect("Failed to construct ISO DateTime.");
let iso_converted = iso_datetime.to_calendar(calendar);


let options = length::Bag::from_date_time_style(length::Date::Medium, length::Time::Short);

let dtf = DateTimeFormatter::try_new(&locale, options.into())
    .expect("Failed to create DateTimeFormatter instance.");

let manual_value = dtf.format(&manual_datetime).expect("Calendars should match");
assert_writeable_eq!(manual_value, "Mar 28, 15 Heisei, 12:33 PM");

let converted_value = dtf.format(&iso_converted).expect("Calendars should match");
assert_writeable_eq!(converted_value, "Sep 1, 2 Reiwa, 12:34 PM");

This model replicates that of ICU and ECMA402.

Implementations

impl DateTimeFormatter

pub fn try_new( locale: &DataLocale, options: DateTimeFormatterOptions, ) -> Result<Self, DateTimeError>

Construct a new DateTimeFormatter from compiled data.

This method will pick the calendar off of the locale; and if unspecified or unknown will fall back to the default calendar for the locale. See AnyCalendarKind for a list of supported calendars.

✨ Enabled with the compiled_data Cargo feature.

📚 Help choosing a constructor

Examples

use icu::calendar::DateTime;
use icu::datetime::{options::length, DateTimeFormatter};
use icu::locid::locale;
use writeable::assert_writeable_eq;

let options = length::Bag::from_date_time_style(
    length::Date::Medium,
    length::Time::Short,
);
let locale = locale!("en-u-ca-gregory").into();

let dtf = DateTimeFormatter::try_new(&locale, options.into())
    .expect("Failed to create TypedDateTimeFormatter instance.");

let datetime = DateTime::try_new_iso_datetime(2020, 9, 1, 12, 34, 28)
    .expect("Failed to construct DateTime.");
let any_datetime = datetime.to_any();

assert_writeable_eq!(
    dtf.format(&any_datetime).expect("Calendars should match"),
    "Sep 1, 2020, 12:34 PM"
);

✨ Enabled with the compiled_data Cargo feature.

📚 Help choosing a constructor

pub fn try_new_with_any_provider( provider: &impl AnyProvider, locale: &DataLocale, options: DateTimeFormatterOptions, ) -> Result<Self, DateTimeError>

A version of Self::try_new that uses custom data provided by an AnyProvider.

📚 Help choosing a constructor

pub fn try_new_with_buffer_provider( provider: &impl BufferProvider, locale: &DataLocale, options: DateTimeFormatterOptions, ) -> Result<Self, DateTimeError>

A version of Self::try_new that uses custom data provided by a BufferProvider.

✨ Enabled with the serde feature.

📚 Help choosing a constructor

pub fn try_new_experimental_unstable<P>( provider: &P, locale: &DataLocale, options: DateTimeFormatterOptions, ) -> Result<Self, DateTimeError>

where P: DataProvider<TimeSymbolsV1Marker> + DataProvider<TimeLengthsV1Marker> + DataProvider<DateSkeletonPatternsV1Marker> + DataProvider<OrdinalV1Marker> + DataProvider<WeekDataV1Marker> + DataProvider<DecimalSymbolsV1Marker> + DataProvider<BuddhistDateLengthsV1Marker> + DataProvider<BuddhistDateSymbolsV1Marker> + DataProvider<ChineseCacheV1Marker> + DataProvider<ChineseDateLengthsV1Marker> + DataProvider<ChineseDateSymbolsV1Marker> + DataProvider<CopticDateLengthsV1Marker> + DataProvider<CopticDateSymbolsV1Marker> + DataProvider<DangiCacheV1Marker> + DataProvider<DangiDateLengthsV1Marker> + DataProvider<DangiDateSymbolsV1Marker> + DataProvider<EthiopianDateLengthsV1Marker> + DataProvider<EthiopianDateSymbolsV1Marker> + DataProvider<GregorianDateLengthsV1Marker> + DataProvider<GregorianDateSymbolsV1Marker> + DataProvider<HebrewDateLengthsV1Marker> + DataProvider<HebrewDateSymbolsV1Marker> + DataProvider<IndianDateLengthsV1Marker> + DataProvider<IndianDateSymbolsV1Marker> + DataProvider<IslamicDateLengthsV1Marker> + DataProvider<IslamicDateSymbolsV1Marker> + DataProvider<IslamicObservationalCacheV1Marker> + DataProvider<IslamicUmmAlQuraCacheV1Marker> + DataProvider<JapaneseDateLengthsV1Marker> + DataProvider<JapaneseDateSymbolsV1Marker> + DataProvider<JapaneseErasV1Marker> + DataProvider<JapaneseExtendedDateLengthsV1Marker> + DataProvider<JapaneseExtendedDateSymbolsV1Marker> + DataProvider<JapaneseExtendedErasV1Marker> + DataProvider<PersianDateLengthsV1Marker> + DataProvider<PersianDateSymbolsV1Marker> + DataProvider<RocDateLengthsV1Marker> + DataProvider<RocDateSymbolsV1Marker> + ?Sized,

A version of Self::try_new_experimental that uses custom data provided by a DataProvider.

📚 Help choosing a constructor

⚠️ The bounds on provider may change over time, including in SemVer minor releases.

pub fn try_new_experimental( locale: &DataLocale, options: DateTimeFormatterOptions, ) -> Result<Self, DateTimeError>

Constructor that supports experimental options with compiled data.

✨ Enabled with the compiled_data and experimental Cargo features.

📚 Help choosing a constructor

🚧 This code is experimental; it may change at any time, in breaking or non-breaking ways, including in SemVer minor releases. It can be enabled with the "experimental" Cargo feature of the icu meta-crate. Use with caution. #1317

Examples

use icu::calendar::DateTime;
use icu::datetime::{options::components, DateTimeFormatter};
use icu::locid::locale;
use writeable::assert_writeable_eq;

let mut options = components::Bag::default();
options.year = Some(components::Year::Numeric);
options.month = Some(components::Month::Long);

let dtf = DateTimeFormatter::try_new_experimental(
    &locale!("en-u-ca-gregory").into(),
    options.into(),
)
.expect("Failed to create TypedDateTimeFormatter instance.");

let datetime = DateTime::try_new_iso_datetime(2020, 9, 1, 12, 34, 28)
    .expect("Failed to construct DateTime.");
let any_datetime = datetime.to_any();

assert_writeable_eq!(
    dtf.format(&any_datetime).expect("Calendars should match"),
    "September 2020"
);

pub fn try_new_unstable<P>( provider: &P, locale: &DataLocale, options: DateTimeFormatterOptions, ) -> Result<Self, DateTimeError>

where P: DataProvider<TimeSymbolsV1Marker> + DataProvider<TimeLengthsV1Marker> + DataProvider<OrdinalV1Marker> + DataProvider<WeekDataV1Marker> + DataProvider<DecimalSymbolsV1Marker> + DataProvider<BuddhistDateLengthsV1Marker> + DataProvider<BuddhistDateSymbolsV1Marker> + DataProvider<ChineseCacheV1Marker> + DataProvider<ChineseDateLengthsV1Marker> + DataProvider<ChineseDateSymbolsV1Marker> + DataProvider<CopticDateLengthsV1Marker> + DataProvider<CopticDateSymbolsV1Marker> + DataProvider<DangiCacheV1Marker> + DataProvider<DangiDateLengthsV1Marker> + DataProvider<DangiDateSymbolsV1Marker> + DataProvider<EthiopianDateLengthsV1Marker> + DataProvider<EthiopianDateSymbolsV1Marker> + DataProvider<GregorianDateLengthsV1Marker> + DataProvider<GregorianDateSymbolsV1Marker> + DataProvider<HebrewDateLengthsV1Marker> + DataProvider<HebrewDateSymbolsV1Marker> + DataProvider<IndianDateLengthsV1Marker> + DataProvider<IndianDateSymbolsV1Marker> + DataProvider<IslamicDateLengthsV1Marker> + DataProvider<IslamicDateSymbolsV1Marker> + DataProvider<JapaneseDateLengthsV1Marker> + DataProvider<JapaneseDateSymbolsV1Marker> + DataProvider<JapaneseErasV1Marker> + DataProvider<JapaneseExtendedDateLengthsV1Marker> + DataProvider<JapaneseExtendedDateSymbolsV1Marker> + DataProvider<JapaneseExtendedErasV1Marker> + DataProvider<IslamicObservationalCacheV1Marker> + DataProvider<IslamicUmmAlQuraCacheV1Marker> + DataProvider<PersianDateLengthsV1Marker> + DataProvider<PersianDateSymbolsV1Marker> + DataProvider<RocDateLengthsV1Marker> + DataProvider<RocDateSymbolsV1Marker> + ?Sized,

A version of Self::try_new that uses custom data provided by a DataProvider.

📚 Help choosing a constructor

⚠️ The bounds on provider may change over time, including in SemVer minor releases.

pub fn try_from_date_and_time( date: DateFormatter, time: TimeFormatter, ) -> Result<Self, DateTimeError>

Constructor that takes a TimeFormatter and DateFormatter and combines them into a DateTimeFormatter. Prefer using one of the other constructors if possible.

Examples

use icu::calendar::DateTime;
use icu::datetime::{
    options::length, DateFormatter, DateTimeFormatter, TimeFormatter,
};
use icu::locid::locale;
use writeable::assert_writeable_eq;

let df = DateFormatter::try_new_with_length(
    &locale!("en-u-ca-gregory").into(),
    length::Date::Medium,
)
.expect("Failed to create TypedDateFormatter instance.");

let tf = TimeFormatter::try_new_with_length(
    &locale!("en").into(),
    length::Time::Short,
)
.expect("Failed to create TimeFormatter instance.");

let dtf = DateTimeFormatter::try_from_date_and_time(df, tf).unwrap();

let datetime = DateTime::try_new_iso_datetime(2020, 9, 1, 12, 34, 28)
    .expect("Failed to construct DateTime.");
let any_datetime = datetime.to_any();

assert_writeable_eq!(
    dtf.format(&any_datetime).expect("Calendars should match"),
    "Sep 1, 2020, 12:34 PM"
);

pub fn format<'l, T>( &'l self, value: &T, ) -> Result<FormattedDateTime<'l>, DateTimeError>

where T: DateTimeInput<Calendar = AnyCalendar>,

Takes a DateTimeInput implementer and returns an instance of a FormattedDateTime that contains all information necessary to display a formatted date and operate on it.

This function will fail if the date passed in uses a different calendar than that of the AnyCalendar. Please convert dates before passing them in if necessary. This function will automatically convert and format dates that are associated with the ISO calendar.

pub fn format_to_string( &self, value: &impl DateTimeInput<Calendar = AnyCalendar>, ) -> Result<String, DateTimeError>

Takes a DateTimeInput implementer and returns it formatted as a string.

This function will fail if the date passed in uses a different calendar than that of the AnyCalendar. Please convert dates before passing them in if necessary. This function will automatically convert and format dates that are associated with the ISO calendar.

pub fn resolve_components(&self) -> Bag

Returns a components::Bag that represents the resolved components for the options that were provided to the DateTimeFormatter. The developer may request a certain set of options for a DateTimeFormatter but the locale and resolution algorithm may change certain details of what actually gets resolved.

✨ Enabled with the experimental Cargo feature.

🚧 This code is experimental; it may change at any time, in breaking or non-breaking ways, including in SemVer minor releases. It can be enabled with the "experimental" Cargo feature of the icu meta-crate. Use with caution. #1317

Examples

use icu::datetime::{
    options::{components, length},
    DateTimeFormatter,
};
use icu::locid::locale;

let options = length::Bag::from_date_style(length::Date::Medium).into();

let dtf =
    DateTimeFormatter::try_new(&locale!("en-u-ca-gregory").into(), options)
        .expect("Failed to create TypedDateTimeFormatter instance.");

let mut expected_components_bag = components::Bag::default();
expected_components_bag.year = Some(components::Year::Numeric);
expected_components_bag.month = Some(components::Month::Short);
expected_components_bag.day = Some(components::Day::NumericDayOfMonth);

assert_eq!(dtf.resolve_components(), expected_components_bag);

Trait Implementations

impl Debug for DateTimeFormatter

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.