com.google.gwt.i18n.shared

## Class DateTimeFormat

- java.lang.Object
- - com.google.gwt.i18n.shared.DateTimeFormat

- Direct Known Subclasses:
    DateTimeFormat

      public class DateTimeFormat
      extends java.lang.Object

  Formats and parses dates and times using locale-sensitive patterns.

  ### Patterns

  Symbol | Meaning | Presentation | Example
  --- | --- | --- | ---
  `G` | era designator | Text | `AD`
  `y` | year | Number | `1996`
  `L` | standalone month in year | Text or Number | `July (or) 07`
  `M` | month in year | Text or Number | `July (or) 07`
  `d` | day in month | Number | `10`
  `h` | hour in am/pm (1-12) | Number | `12`
  `H` | hour in day (0-23) | Number | `0`
  `m` | minute in hour | Number | `30`
  `s` | second in minute | Number | `55`
  `S` | fractional second | Number | `978`
  `E` | day of week | Text | `Tuesday`
  `c` | standalone day of week | Text | `Tuesday`
  `a` | am/pm marker | Text | `PM`
  `k` | hour in day (1-24) | Number | `24`
  `K` | hour in am/pm (0-11) | Number | `0`
  `z` | time zone | Text | `Pacific Standard Time(see comment)`
  `Z` | time zone (RFC 822) | Text | `-0800(See comment)`
  `v` | time zone id | Text | `America/Los_Angeles(See comment)`
  `'` | escape for text | Delimiter | `'Date='`
  `''` | single quote | Literal | `'o''clock'`

  The number of pattern letters influences the format, as follows:

  Text
    if 4 or more, then use the full form; if less than 4, use short or abbreviated form if it exists (e.g., `"EEEE"` produces `"Monday"`, `"EEE"` produces `"Mon"`)
  Number
    the minimum number of digits. Shorter numbers are zero-padded to this amount (e.g. if `"m"` produces `"6"`, `"mm"` produces `"06"`). Year is handled specially; that is, if the count of 'y' is 2, the Year will be truncated to 2 digits. (e.g., if `"yyyy"` produces `"1997"`, `"yy"` produces `"97"`.) Unlike other fields, fractional seconds are padded on the right with zero.
  Text or Number
    3 or more, use text, otherwise use number. (e.g. `"M"` produces `"1"`, `"MM"` produces `"01"`, `"MMM"` produces `"Jan"`, and `"MMMM"` produces `"January"`. Some pattern letters also treat a count of 5 specially, meaning a single-letter abbreviation: `L`, `M`, `E`, and `c`.

  Any characters in the pattern that are not in the ranges of ['`a` '..'`z`'] and ['`A`'..'`Z`'] will be treated as quoted text. For instance, characters like '`:`', ' `.`', '`` ' (space), '`#`' and ' `@`' will appear in the resulting time text even they are not embraced within single quotes.

  [Time Zone Handling] Web browsers don't provide all the information we need for proper time zone formating -- so GWT has a copy of the required data, for your convenience. For simpler cases, one can also use a fallback implementation that only keeps track of the current timezone offset. These two approaches are called, respectively, Common TimeZones and Simple TimeZones, although both are implemented with the same TimeZone class. "TimeZone createTimeZone(String timezoneData)" returns a Common TimeZone object, and "TimeZone createTimeZone(int timeZoneOffsetInMinutes)" returns a Simple TimeZone object. The one provided by OS fall into to Simple TimeZone category. For formatting purpose, following table shows the behavior of GWT DateTimeFormat.

  Pattern | Common TimeZone | Simple TimeZone
  --- | --- | ---
  z, zz, zzz | PDT | UTC-7
  zzzz | Pacific Daylight Time | UTC-7
  Z, ZZ | -0700 | -0700
  ZZZ | -07:00 | -07:00
  ZZZZ | GMT-07:00 | GMT-07:00
  v, vv, vvv, vvvv | America/Los_Angeles | Etc/GMT+7

  ### Parsing Dates and Times

  The pattern does not need to specify every field. If the year, month, or day is missing from the pattern, the corresponding value will be taken from the current date. If the month is specified but the day is not, the day will be constrained to the last day within the specified month. If the hour, minute, or second is missing, the value defaults to zero.

  As with formatting (described above), the count of pattern letters determines the parsing behavior.

  Text
    4 or more pattern letters--use full form, less than 4--use short or abbreviated form if one exists. In parsing, we will always try long format, then short.
  Number
    the minimum number of digits.
  Text or Number
    3 or more characters means use text, otherwise use number

  Although the current pattern specification doesn't not specify behavior for all letters, it may in the future. It is strongly discouraged to use unspecified letters as literal text without quoting them.

  [Note on TimeZone] The time zone support for parsing is limited. Only standard GMT and RFC format are supported. Time zone specification using time zone id (like America/Los_Angeles), time zone names (like PST, Pacific Standard Time) are not supported. Normally, it is too much a burden for a client application to load all the time zone symbols. And in almost all those cases, it is a better choice to do such parsing on server side through certain RPC mechanism. This decision is based on particular use cases we have studied; in principle, it could be changed in future versions.

  ### Examples

  Pattern | Formatted Text
  --- | ---
  `"yyyy.MM.dd G 'at' HH:mm:ss vvvv"` | `1996.07.10 AD at 15:08:56 America/Los_Angeles`
  `"EEE, MMM d, ''yy"` | `Wed, July 10, '96`
  `"h:mm a"` | `12:08 PM`
  `"hh 'o''clock' a, zzzz"` | `12 o'clock PM, Pacific Daylight Time`
  `"K:mm a, vvvv"` | `0:00 PM, America/Los_Angeles`
  `"yyyyy.MMMMM.dd GGG hh:mm aaa"` | `01996.July.10 AD 12:08 PM`

  ### Additional Parsing Considerations

  When parsing a date string using the abbreviated year pattern ( `"yy"`), the parser must interpret the abbreviated year relative to some century. It does this by adjusting dates to be within 80 years before and 20 years after the time the parser instance is created. For example, using a pattern of `"MM/dd/yy"` and a `DateTimeFormat` object created on Jan 1, 1997, the string `"01/11/12"` would be interpreted as Jan 11, 2012 while the string `"05/04/64"` would be interpreted as May 4, 1964. During parsing, only strings consisting of exactly two digits, as defined by `Character.isDigit(char)`, will be parsed into the default century. If the year pattern does not have exactly two 'y' characters, the year is interpreted literally, regardless of the number of digits. For example, using the pattern `"MM/dd/yyyy"`, "01/11/12" parses to Jan 11, 12 A.D.

  When numeric fields abut one another directly, with no intervening delimiter characters, they constitute a run of abutting numeric fields. Such runs are parsed specially. For example, the format "HHmmss" parses the input text "123456" to 12:34:56, parses the input text "12345" to 1:23:45, and fails to parse "1234". In other words, the leftmost field of the run is flexible, while the others keep a fixed width. If the parse fails anywhere in the run, then the leftmost field is shortened by one character, and the entire run is parsed again. This is repeated until either the parse succeeds or the leftmost field is one character in length. If the parse still fails at that point, the parse of the run fails.

  In the current implementation, timezone parsing only supports `GMT:hhmm`, `GMT:+hhmm`, and `GMT:-hhmm`.

  ### Example

  >     public class DateTimeFormatExample implements EntryPoint {

  >       public void onModuleLoad() {
  >         Date today = new Date();

  >         // prints Tue Dec 18 12:01:26 GMT-500 2007 in the default locale.
  >         GWT.log(today.toString());

  >         // prints 12/18/07 in the default locale
  >         GWT.log(DateTimeFormat.getShortDateFormat().format(today));

  >         // prints December 18, 2007 in the default locale
  >         GWT.log(DateTimeFormat.getLongDateFormat().format(today));

  >         // prints 12:01 PM in the default locale
  >         GWT.log(DateTimeFormat.getShortTimeFormat().format(today));

  >         // prints 12:01:26 PM GMT-05:00 in the default locale
  >         GWT.log(DateTimeFormat.getLongTimeFormat().format(today));

  >         // prints Dec 18, 2007 12:01:26 PM in the default locale
  >         GWT.log(DateTimeFormat.getMediumDateTimeFormat().format(today));

  >         // A custom date format
  >         DateTimeFormat fmt = DateTimeFormat.getFormat("EEEE, MMMM dd, yyyy");
  >         // prints Monday, December 17, 2007 in the default locale
  >         GWT.log(fmt.format(today));
  >       }
  >     }

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `static class` | `DateTimeFormat.PredefinedFormat` Predefined date/time formats -- see `CustomDateTimeFormat` if you need some format that isn't supplied here.

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected static java.lang.String` | `ISO8601_PATTERN`
    `protected static java.lang.String` | `RFC2822_PATTERN`

  - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `DateTimeFormat(java.lang.String pattern)` Constructs a format object using the specified pattern and the date time constants for the default locale.
    `protected` | `DateTimeFormat(java.lang.String pattern, DateTimeFormatInfo dtfi)` Constructs a format object using the specified pattern and user-supplied date time constants.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected TimeZone` | `createTimeZone(int timezoneOffset)`
    `java.lang.String` | `format(java.util.Date date)` Format a date object.
    `java.lang.String` | `format(java.util.Date date, TimeZone timeZone)` Format a date object using specified time zone.
    `static DateTimeFormat` | `getFormat(DateTimeFormat.PredefinedFormat predef)` Get a DateTimeFormat instance for a predefined format.
    `static DateTimeFormat` | `getFormat(java.lang.String pattern)` Returns a DateTimeFormat object using the specified pattern.
    `protected static DateTimeFormat` | `getFormat(java.lang.String pattern, DateTimeFormatInfo dtfi)` Internal factory method that provides caching.
    `java.lang.String` | `getPattern()` Retrieve the pattern used in this DateTimeFormat object.
    `java.util.Date` | `parse(java.lang.String text)` Parses text to produce a `Date` value.
    `int` | `parse(java.lang.String text, int start, java.util.Date date)` This method modifies a `Date` object to reflect the date that is parsed from an input string.
    `java.util.Date` | `parseStrict(java.lang.String text)` Parses text to produce a `Date` value.
    `int` | `parseStrict(java.lang.String text, int start, java.util.Date date)` This method modifies a `Date` object to reflect the date that is parsed from an input string.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### RFC2822_PATTERN

          protected static final java.lang.String RFC2822_PATTERN

      See Also:
        Constant Field Values

    - #### ISO8601_PATTERN

          protected static final java.lang.String ISO8601_PATTERN

      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### DateTimeFormat

          protected DateTimeFormat(java.lang.String pattern)

      Constructs a format object using the specified pattern and the date time constants for the default locale.
      Parameters:
        `pattern` - string pattern specification

    - #### DateTimeFormat

          protected DateTimeFormat(java.lang.String pattern,
                        DateTimeFormatInfo dtfi)

      Constructs a format object using the specified pattern and user-supplied date time constants.
      Parameters:
        `pattern` - string pattern specification
        `dtfi` - DateTimeFormatInfo instance to use

  - ### Method Detail

    - #### getFormat

          public static DateTimeFormat getFormat(DateTimeFormat.PredefinedFormat predef)

      Get a DateTimeFormat instance for a predefined format.

      See `CustomDateTimeFormat` if you need a localized format that is not supported here.

      Parameters:
        `predef` - `DateTimeFormat.PredefinedFormat` describing desired format
      Returns:
        a DateTimeFormat instance for the specified format

    - #### getFormat

          public static DateTimeFormat getFormat(java.lang.String pattern)

      Returns a DateTimeFormat object using the specified pattern. If you need to format or parse repeatedly using the same pattern, it is highly recommended that you cache the returned `DateTimeFormat` object and reuse it rather than calling this method repeatedly.

      Note that the pattern supplied is used as-is -- for example, if you supply "MM/dd/yyyy" as the pattern, that is the order you will get the fields, even in locales where the order is different. It is recommended to use `getFormat(PredefinedFormat)` instead -- if you use this method, you are taking responsibility for localizing the patterns yourself.

      Parameters:
        `pattern` - string to specify how the date should be formatted
      Returns:
        a `DateTimeFormat` object that can be used for format or parse date/time values matching the specified pattern
      Throws:
        `java.lang.IllegalArgumentException` - if the specified pattern could not be parsed

    - #### getFormat

          protected static DateTimeFormat getFormat(java.lang.String pattern,
                                 DateTimeFormatInfo dtfi)

      Internal factory method that provides caching.
      Parameters:
        `pattern` -
        `dtfi` -
      Returns:
        DateTimeFormat instance

    - #### format

          public java.lang.String format(java.util.Date date)

      Format a date object.
      Parameters:
        `date` - the date object being formatted
      Returns:
        string representation for this date in desired format

    - #### format

          public java.lang.String format(java.util.Date date,
                                TimeZone timeZone)

      Format a date object using specified time zone.
      Parameters:
        `date` - the date object being formatted
        `timeZone` - a TimeZone object that holds time zone information, or `null` to use the default
      Returns:
        string representation for this date in the format defined by this object

    - #### getPattern

          public java.lang.String getPattern()

      Retrieve the pattern used in this DateTimeFormat object.
      Returns:
        pattern string

    - #### parse

          public java.util.Date parse(java.lang.String text)
                               throws java.lang.IllegalArgumentException

      Parses text to produce a `Date` value. An `IllegalArgumentException` is thrown if either the text is empty or if the parse does not consume all characters of the text. Dates are parsed leniently, so invalid dates will be wrapped around as needed. For example, February 30 will wrap to March 2.
      Parameters:
        `text` - the string being parsed
      Returns:
        a parsed date/time value
      Throws:
        `java.lang.IllegalArgumentException` - if the entire text could not be converted into a number

    - #### parse

          public int parse(java.lang.String text,
                  int start,
                  java.util.Date date)

      This method modifies a `Date` object to reflect the date that is parsed from an input string. Dates are parsed leniently, so invalid dates will be wrapped around as needed. For example, February 30 will wrap to March 2.
      Parameters:
        `text` - the string that need to be parsed
        `start` - the character position in "text" where parsing should start
        `date` - the date object that will hold parsed value
      Returns:
        0 if parsing failed, otherwise the number of characters advanced

    - #### parseStrict

          public java.util.Date parseStrict(java.lang.String text)
                                     throws java.lang.IllegalArgumentException

      Parses text to produce a `Date` value. An `IllegalArgumentException` is thrown if either the text is empty or if the parse does not consume all characters of the text. Dates are parsed strictly, so invalid dates will result in an `IllegalArgumentException`.
      Parameters:
        `text` - the string being parsed
      Returns:
        a parsed date/time value
      Throws:
        `java.lang.IllegalArgumentException` - if the entire text could not be converted into a number

    - #### parseStrict

          public int parseStrict(java.lang.String text,
                        int start,
                        java.util.Date date)

      This method modifies a `Date` object to reflect the date that is parsed from an input string. Dates are parsed strictly, so invalid dates will return 0. For example, February 30 will return 0 because February only has 28 days.
      Parameters:
        `text` - the string that need to be parsed
        `start` - the character position in "text" where parsing should start
        `date` - the date object that will hold parsed value
      Returns:
        0 if parsing failed, otherwise the number of characters advanced

    - #### createTimeZone

          protected TimeZone createTimeZone(int timezoneOffset)

      Parameters:
        `timezoneOffset` -
      Returns:
        `TimeZone` instance