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ICU 77.1: icu::DateFormat Class Reference

DateFormat is an abstract class for a family of classes that convert dates and times from their internal representations to textual form and back again in a language-independent manner. More...

#include <datefmt.h>

DateFormat is an abstract class for a family of classes that convert dates and times from their internal representations to textual form and back again in a language-independent manner.

Converting from the internal representation (milliseconds since midnight, January 1, 1970) to text is known as "formatting," and converting from text to millis is known as "parsing." We currently define only one concrete subclass of DateFormat: SimpleDateFormat, which can handle pretty much all normal date formatting and parsing actions.

DateFormat helps you to format and parse dates for any locale. Your code can be completely independent of the locale conventions for months, days of the week, or even the calendar format: lunar vs. solar.

To format a date for the current Locale, use one of the static factory methods:

UnicodeString myString;
myString = dfmt->format( myDate, myString );
static UDate getNow()
Returns the current UTC (GMT) time measured in milliseconds since 0:00:00 on 1/1/70 (derived from the...
DateFormat()
Default constructor.
static DateFormat * createDateInstance(EStyle style=kDefault, const Locale &aLocale=Locale::getDefault())
Creates a date formatter with the given formatting style for the given const locale.
double UDate
Date and Time data type.

If you are formatting multiple numbers, it is more efficient to get the format and use it multiple times so that the system doesn't have to fetch the information about the local language and country conventions multiple times.

UnicodeString myString;
UDate
 myDateArr[] = { 0.0, 100000000.0, 2000000000.0 }; 
for (int32_t i = 0; i < 3; ++i) {
    myString.remove();
    cout << df->format( myDateArr[i], myString ) << endl;
}

To get specific fields of a date, you can use UFieldPosition to get specific fields.

FieldPosition pos(DateFormat::YEAR_FIELD);
UnicodeString myString;
myString = dfmt->format( myDate, myString );
cout << myString << endl;
cout << pos.getBeginIndex() << "," << pos. getEndIndex() << endl;

To format a date for a different Locale, specify it in the call to createDateInstance().

static const Locale & getFrance()
Useful constant for this country/region.

You can use a DateFormat to parse also.

UDate
 myDate = df->parse(myString, status);
UErrorCode
Standard ICU4C error code type, a substitute for exceptions.
@ U_ZERO_ERROR
No error, no warning.

Use createDateInstance() to produce the normal date format for that country. There are other static factory methods available. Use createTimeInstance() to produce the normal time format for that country. Use createDateTimeInstance() to produce a DateFormat that formats both date and time. You can pass in different options to these factory methods to control the length of the result; from SHORT to MEDIUM to LONG to FULL. The exact result depends on the locale, but generally:

• SHORT is completely numeric, such as 12/13/52 or 3:30pm
• MEDIUM is longer, such as Jan 12, 1952
• LONG is longer, such as January 12, 1952 or 3:30:32pm
• FULL is pretty completely specified, such as Tuesday, April 12, 1952 AD or 3:30:42pm PST.

You can also set the time zone on the format if you wish. If you want even more control over the format or parsing, (or want to give your users more control), you can try casting the DateFormat you get from the factory methods to a SimpleDateFormat. This will work for the majority of countries; just remember to check getDynamicClassID() before carrying out the cast.

You can also use forms of the parse and format methods with ParsePosition and FieldPosition to allow you to

• Progressively parse through pieces of a string.
• Align any particular field, or find out where it is for selection on the screen.

User subclasses are not supported. While clients may write subclasses, such code will not necessarily work and will not be guaranteed to work stably from release to release.

Definition at line 156 of file datefmt.h.

Constants for various style patterns.

These reflect the order of items in the DateTimePatterns resource. There are 4 time patterns, 4 date patterns, the default date-time pattern, and 4 date-time patterns. Each block of 4 values in the resource occurs in the order full, long, medium, short.

Stable:

ICU 2.4

These constants are provided for backwards compatibility only.

Please use the C++ style constants defined above.

Definition at line 166 of file datefmt.h.

Default constructor.

Creates a DateFormat with no Calendar or NumberFormat associated with it. This constructor depends on the subclasses to fill in the calendar and numberFormat fields.

Stable:

ICU 2.0

Set the calendar to be used by this date format.

Initially, the default calendar for the specified or default locale is used. The caller should not delete the Calendar object after it is adopted by this call. Adopting a new calendar will change to the default symbols.

Parameters

calendarToAdopt Calendar object to be adopted.

Stable:

ICU 2.0

Reimplemented in icu::SimpleDateFormat.

Sets the time zone for the calendar of this DateFormat object.

The caller no longer owns the TimeZone object and should not delete it after this call.

Parameters

Stable:

ICU 2.0

Clones this object polymorphically.

The caller owns the result and should delete it when done.

Returns

clone, or nullptr if an error occurred

Stable:

ICU 2.0

Implements icu::Format.

Implemented in icu::SimpleDateFormat.

Creates a date formatter with the given formatting style for the given const locale.

Parameters

style The given formatting style. For example, SHORT for "M/d/yy" in the US locale. As currently implemented, relative date formatting only affects a limited range of calendar days before or after the current date, based on the CLDR <field type="day">/<relative> data: For example, in English, "Yesterday", "Today", and "Tomorrow". Outside of this range, dates are formatted using the corresponding non-relative style. aLocale The given locale.

Returns

A date formatter which the caller owns.

Stable:

ICU 2.0

Creates a date/time formatter with the given formatting styles for the given locale.

Parameters

dateStyle The given formatting style for the date portion of the result. For example, SHORT for "M/d/yy" in the US locale. As currently implemented, relative date formatting only affects a limited range of calendar days before or after the current date, based on the CLDR <field type="day">/<relative> data: For example, in English, "Yesterday", "Today", and "Tomorrow". Outside of this range, dates are formatted using the corresponding non-relative style. timeStyle The given formatting style for the time portion of the result. For example, SHORT for "h:mm a" in the US locale. Relative time styles are not currently supported. aLocale The given locale.

Returns

A date/time formatter which the caller owns.

Stable:

ICU 2.0

Create a default date/time formatter that uses the SHORT style for both the date and the time.

Returns

A date/time formatter which the caller owns.

Stable:

ICU 2.0

Creates a date/time formatter for the given skeleton and locale.

Parameters

calendarToAdopt the calendar returned DateFormat is to use. skeleton The skeleton e.g "yMMMMd." Fields in the skeleton can be in any order, and this method uses the locale to map the skeleton to a pattern that includes locale specific separators with the fields in the appropriate order for that locale. locale The given locale. status Any error returned here.

Returns

A date/time formatter which the caller owns.

Stable:

ICU 55

Creates a date/time formatter for the given skeleton and locale.

Parameters

skeleton The skeleton e.g "yMMMMd." Fields in the skeleton can be in any order, and this method uses the locale to map the skeleton to a pattern that includes locale specific separators with the fields in the appropriate order for that locale. locale The given locale. status Any error returned here.

Returns

A date/time formatter which the caller owns.

Stable:

ICU 55

Creates a date/time formatter for the given skeleton and default locale.

Parameters

skeleton The skeleton e.g "yMMMMd." Fields in the skeleton can be in any order, and this method uses the locale to map the skeleton to a pattern that includes locale specific separators with the fields in the appropriate order for that locale. status Any error returned here.

Returns

A date/time formatter which the caller owns.

Stable:

ICU 55

Creates a time formatter with the given formatting style for the given locale.

Parameters

style The given formatting style. For example, SHORT for "h:mm a" in the US locale. Relative time styles are not currently supported. aLocale The given locale.

Returns

A time formatter which the caller owns.

Stable:

ICU 2.0

Formats a date into a date/time string.

This is an abstract method which concrete subclasses must implement.

On input, the FieldPosition parameter may have its "field" member filled with an enum value specifying a field. On output, the FieldPosition will be filled in with the text offsets for that field.

For example, given a time text "1996.07.10 AD at 15:08:56 PDT", if the given fieldPosition.field is UDAT_YEAR_FIELD, the offsets fieldPosition.beginIndex and statfieldPositionus.getEndIndex will be set to 0 and 4, respectively.

Notice that if the same time field appears more than once in a pattern, the status will be set for the first occurrence of that time field. For instance, formatting a UDate to the time string "1 PM PDT (Pacific Daylight Time)" using the pattern "h a z (zzzz)" and the alignment field DateFormat::TIMEZONE_FIELD, the offsets fieldPosition.beginIndex and fieldPosition.getEndIndex will be set to 5 and 8, respectively, for the first occurrence of the timezone pattern character 'z'.

Parameters

cal Calendar set to the date and time to be formatted into a date/time string. When the calendar type is different from the internal calendar held by this DateFormat instance, the date and the time zone will be inherited from the input calendar, but other calendar field values will be calculated by the internal calendar. appendTo Output parameter to receive result. Result is appended to existing contents. fieldPosition On input: an alignment field, if desired (see examples above) On output: the offsets of the alignment field (see examples above)

Returns

Reference to 'appendTo' parameter.

Stable:

ICU 2.1

Implemented in icu::SimpleDateFormat.

Formats a date into a date/time string.

Subclasses should implement this method.

Parameters

cal Calendar set to the date and time to be formatted into a date/time string. When the calendar type is different from the internal calendar held by this DateFormat instance, the date and the time zone will be inherited from the input calendar, but other calendar field values will be calculated by the internal calendar. appendTo Output parameter to receive result. Result is appended to existing contents. posIter On return, can be used to iterate over positions of fields generated by this format call. Field values are defined in UDateFormatField. Can be nullptr. status error status.

Returns

Reference to 'appendTo' parameter.

Stable:

ICU 4.4

Reimplemented in icu::SimpleDateFormat.

Format an object to produce a string.

This method handles Formattable objects with a UDate type. If a the Formattable object type is not a Date, then it returns a failing UErrorCode.

Parameters

obj The object to format. Must be a Date. appendTo Output parameter to receive result. Result is appended to existing contents. pos On input: an alignment field, if desired. On output: the offsets of the alignment field. status Output param filled with success/failure status.

Returns

Reference to 'appendTo' parameter.

Stable:

ICU 2.0

Implements icu::Format.

Format an object to produce a string.

This is a pure virtual method which subclasses must implement. This method allows polymorphic formatting of Formattable objects. If a subclass of Format receives a Formattable object type it doesn't handle (e.g., if a numeric Formattable is passed to a DateFormat object) then it returns a failing UErrorCode.

Parameters

obj The object to format. appendTo Output parameter to receive result. Result is appended to existing contents. pos On input: an alignment field, if desired. On output: the offsets of the alignment field. status Output param filled with success/failure status.

Returns

Reference to 'appendTo' parameter.

Stable:

ICU 2.0

Format an object to produce a string.

Subclasses should override this method. This method allows polymorphic formatting of Formattable objects. If a subclass of Format receives a Formattable object type it doesn't handle (e.g., if a numeric Formattable is passed to a DateFormat object) then it returns a failing UErrorCode.

Parameters

obj The object to format. appendTo Output parameter to receive result. Result is appended to existing contents. posIter On return, can be used to iterate over positions of fields generated by this format call. status Output param filled with success/failure status.

Returns

Reference to 'appendTo' parameter.

Stable:

ICU 4.4

Format an object to produce a string.

This method handles Formattable objects with a UDate type. If a the Formattable object type is not a Date, then it returns a failing UErrorCode.

Parameters

obj The object to format. Must be a Date. appendTo Output parameter to receive result. Result is appended to existing contents. posIter On return, can be used to iterate over positions of fields generated by this format call. Field values are defined in UDateFormatField. Can be nullptr. status Output param filled with success/failure status.

Returns

Reference to 'appendTo' parameter.

Stable:

ICU 4.4

Reimplemented from icu::Format.

Formats an object to produce a string.

Parameters

obj The object to format. appendTo Output parameter to receive result. Result is appended to existing contents. status Output parameter filled in with success or failure status.

Returns

Reference to 'appendTo' parameter.

Stable:

ICU 2.0

Formats a UDate into a date/time string.

If there is a problem, you won't know, using this method. Use the overloaded format() method which takes a FieldPosition& to detect formatting problems.

Parameters

date The UDate value to be formatted into a string. appendTo Output parameter to receive result. Result is appended to existing contents.

Returns

Reference to 'appendTo' parameter.

Stable:

ICU 2.0

Formats a UDate into a date/time string.

On input, the FieldPosition parameter may have its "field" member filled with an enum value specifying a field. On output, the FieldPosition will be filled in with the text offsets for that field.

For example, given a time text "1996.07.10 AD at 15:08:56 PDT", if the given fieldPosition.field is UDAT_YEAR_FIELD, the offsets fieldPosition.beginIndex and statfieldPositionus.getEndIndex will be set to 0 and 4, respectively.

Notice that if the same time field appears more than once in a pattern, the status will be set for the first occurrence of that time field. For instance, formatting a UDate to the time string "1 PM PDT (Pacific Daylight Time)" using the pattern "h a z (zzzz)" and the alignment field DateFormat::TIMEZONE_FIELD, the offsets fieldPosition.beginIndex and fieldPosition.getEndIndex will be set to 5 and 8, respectively, for the first occurrence of the timezone pattern character 'z'.

Parameters

date UDate to be formatted into a date/time string. appendTo Output parameter to receive result. Result is appended to existing contents. fieldPosition On input: an alignment field, if desired (see examples above) On output: the offsets of the alignment field (see examples above)

Returns

Reference to 'appendTo' parameter.

Stable:

ICU 2.0

Formats a UDate into a date/time string.

Parameters

date UDate to be formatted into a date/time string. appendTo Output parameter to receive result. Result is appended to existing contents. posIter On return, can be used to iterate over positions of fields generated by this format call. Field values are defined in UDateFormatField. Can be nullptr. status error status.

Returns

Reference to 'appendTo' parameter.

Stable:

ICU 4.4

Gets the set of locales for which DateFormats are installed.

Parameters

count Filled in with the number of locales in the list that is returned.

Returns

the set of locales for which DateFormats are installed. The caller does NOT own this list and must not delete it.

Stable:

ICU 2.0

Returns the best pattern given a skeleton and locale.

Parameters

locale the locale skeleton the skeleton status ICU error returned here

Returns

the best pattern.

Internal:

Do not use. This API is for internal use only. For ICU use only.

Returns a boolean from this DateFormat May return U_UNSUPPORTED_ERROR if this instance does not support the specified attribute.

Parameters

attr the attribute to set status the error type

Returns

the attribute value. Undefined if there is an error.

Stable:

ICU 53

Gets the calendar associated with this date/time formatter.

The calendar is owned by the formatter and must not be modified. Also, the calendar does not reflect the results of a parse operation. To parse to a calendar, use parse(const UnicodeString&, Calendar& cal, ParsePosition&)

Returns

the calendar associated with this date/time formatter.

Stable:

ICU 2.0

Get the formatter's UDisplayContext value for the specified UDisplayContextType, such as UDISPCTX_TYPE_CAPITALIZATION.

Parameters

type The UDisplayContextType whose value to return status Input/output status. If at entry this indicates a failure status, the function will do nothing; otherwise this will be updated with any new status from the function.

Returns

The UDisplayContextValue for the specified type.

Stable:

ICU 53

Gets the number formatter which this date/time formatter uses to format and parse the numeric portions of the pattern.

Returns

the number formatter which this date/time formatter uses.

Stable:

ICU 2.0

Returns whether date/time parsing in the encapsulated Calendar object processing is lenient.

Stable:

ICU 53

Returns whether both date/time parsing in the encapsulated Calendar object and DateFormat whitespace & numeric processing is lenient.

Stable:

ICU 2.0

Default assignment operator.

Stable:

ICU 2.0

Parse a date/time string beginning at the given parse position.

For example, a time text "07/10/96 4:5 PM, PDT" will be parsed into a Date that is equivalent to Date(837039928046).

By default, parsing is lenient: If the input is not in the form used by this object's format method but can still be parsed as a date, then the parse succeeds. Clients may insist on strict adherence to the format by calling setLenient(false).

See also

DateFormat::setLenient(boolean)

Parameters

text The date/time string to be parsed. cal A Calendar set on input to the date and time to be used for missing values in the date/time string being parsed, and set on output to the parsed date/time. When the calendar type is different from the internal calendar held by this DateFormat instance, the internal calendar will be cloned to a work calendar set to the same milliseconds and time zone as the cal parameter, field values will be parsed based on the work calendar, then the result (milliseconds and time zone) will be set in this calendar. pos On input, the position at which to start parsing; on output, the position at which parsing terminated, or the start position if the parse failed.

Stable:

ICU 2.1

Implemented in icu::SimpleDateFormat.

Parse a date/time string beginning at the given parse position.

For example, a time text "07/10/96 4:5 PM, PDT" will be parsed into a Date that is equivalent to Date(837039928046).

By default, parsing is lenient: If the input is not in the form used by this object's format method but can still be parsed as a date, then the parse succeeds. Clients may insist on strict adherence to the format by calling setLenient(false).

See also

DateFormat::setLenient(boolean)

Note that the normal date formats associated with some calendars - such as the Chinese lunar calendar - do not specify enough fields to enable dates to be parsed unambiguously. In the case of the Chinese lunar calendar, while the year within the current 60-year cycle is specified, the number of such cycles since the start date of the calendar (in the ERA field of the Calendar object) is not normally part of the format, and parsing may assume the wrong era. For cases such as this it is recommended that clients parse using the method parse(const UnicodeString&, Calendar& cal, ParsePosition&) with the Calendar passed in set to the current date, or to a date within the era/cycle that should be assumed if absent in the format.

Parameters

text The date/time string to be parsed into a UDate value. pos On input, the position at which to start parsing; on output, the position at which parsing terminated, or the start position if the parse failed.

Returns

A valid UDate if the input could be parsed.

Stable:

ICU 2.0

Parse a date/time string.

For example, a time text "07/10/96 4:5 PM, PDT" will be parsed into a UDate that is equivalent to Date(837039928046). Parsing begins at the beginning of the string and proceeds as far as possible. Assuming no parse errors were encountered, this function doesn't return any information about how much of the string was consumed by the parsing. If you need that information, use the version of parse() that takes a ParsePosition.

By default, parsing is lenient: If the input is not in the form used by this object's format method but can still be parsed as a date, then the parse succeeds. Clients may insist on strict adherence to the format by calling setLenient(false).

See also

DateFormat::setLenient(boolean)

Note that the normal date formats associated with some calendars - such as the Chinese lunar calendar - do not specify enough fields to enable dates to be parsed unambiguously. In the case of the Chinese lunar calendar, while the year within the current 60-year cycle is specified, the number of such cycles since the start date of the calendar (in the ERA field of the Calendar object) is not normally part of the format, and parsing may assume the wrong era. For cases such as this it is recommended that clients parse using the method parse(const UnicodeString&, Calendar& cal, ParsePosition&) with the Calendar passed in set to the current date, or to a date within the era/cycle that should be assumed if absent in the format.

Parameters

text The date/time string to be parsed into a UDate value. status Output param to be set to success/failure code. If 'text' cannot be parsed, it will be set to a failure code.

Returns

The parsed UDate value, if successful.

Stable:

ICU 2.0

Parse a string to produce an object.

This methods handles parsing of date/time strings into Formattable objects with UDate types.

Before calling, set parse_pos.index to the offset you want to start parsing at in the source. After calling, parse_pos.index is the end of the text you parsed. If error occurs, index is unchanged.

When parsing, leading whitespace is discarded (with a successful parse), while trailing whitespace is left as is.

See Format::parseObject() for more.

Parameters

source The string to be parsed into an object. result Formattable to be set to the parse result. If parse fails, return contents are undefined. parse_pos The position to start parsing at. Upon return this param is set to the position after the last character successfully parsed. If the source is not parsed successfully, this param will remain unchanged.

Stable:

ICU 2.0

Implements icu::Format.

Sets an boolean attribute on this DateFormat.

May return U_UNSUPPORTED_ERROR if this instance does not support the specified attribute.

Parameters

attr the attribute to set newvalue new value status the error type

Returns

*this - for chaining (example: format.setAttribute(...).setAttribute(...) )

Stable:

ICU 53

Set the calendar to be used by this date format.

Initially, the default calendar for the specified or default locale is used.

Parameters

Stable:

ICU 2.0

Specifies whether encapsulated Calendar date/time parsing is to be lenient.

With lenient parsing, the parser may use heuristics to interpret inputs that do not precisely match this object's format. Without lenient parsing, inputs must match this object's format more closely.

Parameters

lenient when true, parsing is lenient

See also

com.ibm.icu.util.Calendar::setLenient

Stable:

ICU 53

Set a particular UDisplayContext value in the formatter, such as UDISPCTX_CAPITALIZATION_FOR_STANDALONE.

Parameters

value The UDisplayContext value to set. status Input/output status. If at entry this indicates a failure status, the function will do nothing; otherwise this will be updated with any new status from the function.

Stable:

ICU 53

Reimplemented in icu::SimpleDateFormat.

Specifies whether date/time parsing is to be lenient.

With lenient parsing, the parser may use heuristics to interpret inputs that do not precisely match this object's format. Without lenient parsing, inputs must match this object's format more closely.

Note: ICU 53 introduced finer grained control of leniency (and added new control points) making the preferred method a combination of setCalendarLenient() & setBooleanAttribute() calls. This method supports prior functionality but may not support all future leniency control & behavior of DateFormat. For control of pre 53 leniency,
Calendar and DateFormat whitespace & numeric tolerance, this method is safe to use. However, mixing leniency control via this method and modification of the newer attributes via setBooleanAttribute() may produce undesirable results.

Parameters

lenient True specifies date/time interpretation to be lenient.

See also

Calendar::setLenient

Stable:

ICU 2.0

Allows you to set the number formatter.

Parameters

Stable:

ICU 2.0

Sets the time zone for the calendar of this DateFormat object.

Parameters

Stable:

ICU 2.0

The calendar that DateFormat uses to produce the time field values needed to implement date/time formatting.

Subclasses should generally initialize this to the default calendar for the locale associated with this DateFormat.

Stable:

ICU 2.4

Definition at line 871 of file datefmt.h.

The number formatter that DateFormat uses to format numbers in dates and times.

Subclasses should generally initialize this to the default number format for the locale associated with this DateFormat.

Stable:

ICU 2.4

Definition at line 879 of file datefmt.h.

The documentation for this class was generated from the following file:

• i18n/unicode/datefmt.h

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