# Class SimpleDateFormat

java.lang.Object
java.text.Format
java.text.DateFormat
java.text.SimpleDateFormat

All Implemented Interfaces:
  `Serializable`, `Cloneable`

public class SimpleDateFormat extends DateFormat
`SimpleDateFormat` is a concrete class for formatting and parsing dates in a locale-sensitive manner. It allows for formatting (date → text), parsing (text → date), and normalization.

`SimpleDateFormat` allows you to start by choosing any user-defined patterns for date-time formatting. However, you are encouraged to create a date-time formatter with either `getTimeInstance`, `getDateInstance`, or `getDateTimeInstance` in `DateFormat`. Each of these class methods can return a date/time formatter initialized with a default format pattern. You may modify the format pattern using the `applyPattern` methods as desired. For more information on using these methods, see `DateFormat`.

## Date and Time Patterns

Date and time formats are specified by date and time pattern strings. Within date and time pattern strings, unquoted letters from `'A'` to `'Z'` and from `'a'` to `'z'` are interpreted as pattern letters representing the components of a date or time string. Text can be quoted using single quotes (`'`) to avoid interpretation. `"''"` represents a single quote. All other characters are not interpreted; they're simply copied into the output string during formatting or matched against the input string during parsing.

The following pattern letters are defined (all other characters from `'A'` to `'Z'` and from `'a'` to `'z'` are reserved):

> Chart shows pattern letters, date/time component, presentation, and examples.
> Letter | Date or Time Component | Presentation | Examples
> --- | --- | --- | ---
> `G` | Era designator | Text | `AD`
> `y` | Year | Year | `1996`; `96`
> `Y` | Week year | Year | `2009`; `09`
> `M` | Month in year (context sensitive) | Month | `July`; `Jul`; `07`
> `L` | Month in year (standalone form) | Month | `July`; `Jul`; `07`
> `w` | Week in year | Number | `27`
> `W` | Week in month | Number | `2`
> `D` | Day in year | Number | `189`
> `d` | Day in month | Number | `10`
> `F` | Day of week in month | Number | `2`
> `E` | Day name in week | Text | `Tuesday`; `Tue`
> `u` | Day number of week (1 = Monday, ..., 7 = Sunday) | Number | `1`
> `a` | Am/pm marker | Text | `PM`
> `H` | Hour in day (0-23) | Number | `0`
> `k` | Hour in day (1-24) | Number | `24`
> `K` | Hour in am/pm (0-11) | Number | `0`
> `h` | Hour in am/pm (1-12) | Number | `12`
> `m` | Minute in hour | Number | `30`
> `s` | Second in minute | Number | `55`
> `S` | Millisecond | Number | `978`
> `z` | Time zone | General time zone | `Pacific Standard Time`; `PST`; `GMT-08:00`
> `Z` | Time zone | RFC 822 time zone | `-0800`
> `X` | Time zone | ISO 8601 time zone | `-08`; `-0800`; `-08:00`

Pattern letters are usually repeated, as their number determines the exact presentation:

- Text: For formatting, if the number of pattern letters is 4 or more, the full form is used; otherwise a short or abbreviated form is used if available. For parsing, both forms are accepted, independent of the number of pattern letters.
- Number: For formatting, the number of pattern letters is the minimum number of digits, and shorter numbers are zero-padded to this amount. For parsing, the number of pattern letters is ignored unless it's needed to separate two adjacent fields.
- Year: If the formatter's `Calendar` is the Gregorian calendar, the following rules are applied.
  - For formatting, if the number of pattern letters is 2, the year is truncated to 2 digits; otherwise it is interpreted as a number.
  - For parsing, if the number of pattern letters is more than 2, the year is interpreted literally, regardless of the number of digits. So using the pattern "MM/dd/yyyy", "01/11/12" parses to Jan 11, 12 A.D.
  - For parsing with the abbreviated year pattern ("y" or "yy"), `SimpleDateFormat` 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 `SimpleDateFormat` instance is created. For example, using a pattern of "MM/dd/yy" and a `SimpleDateFormat` instance 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. Any other numeric string, such as a one digit string, a three or more digit string, or a two digit string that isn't all digits (for example, "-1"), is interpreted literally. So "01/02/3" or "01/02/003" are parsed, using the same pattern, as Jan 2, 3 AD. Likewise, "01/02/-3" is parsed as Jan 2, 4 BC.
  Otherwise, calendar system specific forms are applied. For both formatting and parsing, if the number of pattern letters is 4 or more, a calendar specific long form is used. Otherwise, a calendar specific short or abbreviated form is used.
  If week year `'Y'` is specified and the calendar doesn't support any week years, the calendar year (`'y'`) is used instead. The support of week years can be tested with a call to `getCalendar()`.`isWeekDateSupported()`.
- Month: If the number of pattern letters is 3 or more, the month is interpreted as text; otherwise, it is interpreted as a number.
  - Letter M produces context-sensitive month names, such as the embedded form of names. Letter M is context-sensitive in the sense that when it is used in the standalone pattern, for example, "MMMM", it gives the standalone form of a month name and when it is used in the pattern containing other field(s), for example, "d MMMM", it gives the format form of a month name. For example, January in the Catalan language is "de gener" in the format form while it is "gener" in the standalone form. In this case, "MMMM" will produce "gener" and the month part of the "d MMMM" will produce "de gener". If a `DateFormatSymbols` has been set explicitly with constructor `SimpleDateFormat(String,DateFormatSymbols)` or method `setDateFormatSymbols(DateFormatSymbols)`, the month names given by the `DateFormatSymbols` are used.
  - Letter L produces the standalone form of month names.
- General time zone: Time zones are interpreted as text if they have names. For time zones representing a GMT offset value, the following syntax is used:

           GMTOffsetTimeZone:
                   GMT Sign Hours : Minutes
           Sign: one of
                   + -
           Hours:
                   Digit
                   Digit Digit
           Minutes:
                   Digit Digit
           Digit: one of
                   0 1 2 3 4 5 6 7 8 9

  Hours must be between 0 and 23, and Minutes must be between 00 and 59. The format is locale independent and digits must be taken from the Basic Latin block of the Unicode standard.

  For parsing, RFC 822 time zones are also accepted.

- RFC 822 time zone: For formatting, the RFC 822 4-digit time zone format is used:

           RFC822TimeZone:
                   Sign TwoDigitHours Minutes
           TwoDigitHours:
                   Digit Digit

  TwoDigitHours must be between 00 and 23. Other definitions are as for general time zones.

  For parsing, general time zones are also accepted.

- ISO 8601 Time zone: The number of pattern letters designates the format for both formatting and parsing as follows:

           ISO8601TimeZone:
                   OneLetterISO8601TimeZone
                   TwoLetterISO8601TimeZone
                   ThreeLetterISO8601TimeZone
           OneLetterISO8601TimeZone:
                   Sign TwoDigitHours
                   Z
           TwoLetterISO8601TimeZone:
                   Sign TwoDigitHours Minutes
                   Z
           ThreeLetterISO8601TimeZone:
                   Sign TwoDigitHours : Minutes
                   Z

  Other definitions are as for general time zones or RFC 822 time zones.

  For formatting, if the offset value from GMT is 0, `"Z"` is produced. If the number of pattern letters is 1, any fraction of an hour is ignored. For example, if the pattern is `"X"` and the time zone is `"GMT+05:30"`, `"+05"` is produced.

  For parsing, `"Z"` is parsed as the UTC time zone designator. General time zones are not accepted.

  If the number of pattern letters is 4 or more, `IllegalArgumentException` is thrown when constructing a `SimpleDateFormat` or applying a pattern.

`SimpleDateFormat` also supports localized date and time pattern strings. In these strings, the pattern letters described above may be replaced with other, locale dependent, pattern letters. `SimpleDateFormat` does not deal with the localization of text other than the pattern letters; that's up to the client of the class.

### Examples

The following examples show how date and time patterns are interpreted in the U.S. locale. The given date and time are 2001-07-04 12:08:56 local time in the U.S. Pacific Time time zone.

> Examples of date and time patterns interpreted in the U.S. locale
> Date and Time Pattern | Result
> --- | ---
> `"yyyy.MM.dd G 'at' HH:mm:ss z"` | `2001.07.04 AD at 12:08:56 PDT`
> `"EEE, MMM d, ''yy"` | `Wed, Jul 4, '01`
> `"h:mm a"` | `12:08 PM`
> `"hh 'o''clock' a, zzzz"` | `12 o'clock PM, Pacific Daylight Time`
> `"K:mm a, z"` | `0:08 PM, PDT`
> `"yyyyy.MMMMM.dd GGG hh:mm aaa"` | `02001.July.04 AD 12:08 PM`
> `"EEE, d MMM yyyy HH:mm:ss Z"` | `Wed, 4 Jul 2001 12:08:56 -0700`
> `"yyMMddHHmmssZ"` | `010704120856-0700`
> `"yyyy-MM-dd'T'HH:mm:ss.SSSZ"` | `2001-07-04T12:08:56.235-0700`
> `"yyyy-MM-dd'T'HH:mm:ss.SSSXXX"` | `2001-07-04T12:08:56.235-07:00`
> `"YYYY-'W'ww-u"` | `2001-W27-3`

### Synchronization

Date formats are not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally.

API Note:
  Consider using `DateTimeFormatter` as an immutable and thread-safe alternative.
Since:
  1.1
See Also:
  - Java Tutorial
  - `Calendar`
  - `TimeZone`
  - `DateFormat`
  - `DateFormatSymbols`
  - `DateTimeFormatter`
  - Serialized Form

- ## Nested Class Summary

  ### Nested classes/interfaces declared in class java.text.DateFormat

  `DateFormat.Field`

- ## Field Summary

  ### Fields declared in class java.text.DateFormat

  `AM_PM_FIELD, calendar, DATE_FIELD, DAY_OF_WEEK_FIELD, DAY_OF_WEEK_IN_MONTH_FIELD, DAY_OF_YEAR_FIELD, DEFAULT, ERA_FIELD, FULL, HOUR_OF_DAY0_FIELD, HOUR_OF_DAY1_FIELD, HOUR0_FIELD, HOUR1_FIELD, LONG, MEDIUM, MILLISECOND_FIELD, MINUTE_FIELD, MONTH_FIELD, numberFormat, SECOND_FIELD, SHORT, TIMEZONE_FIELD, WEEK_OF_MONTH_FIELD, WEEK_OF_YEAR_FIELD, YEAR_FIELD`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `SimpleDateFormat()`
  Constructs a `SimpleDateFormat` using the default pattern and date format symbols for the default `FORMAT` locale.
  `SimpleDateFormat(String pattern)`
  Constructs a `SimpleDateFormat` using the given pattern and the default date format symbols for the default `FORMAT` locale.
  `SimpleDateFormat(String pattern, DateFormatSymbols formatSymbols)`
  Constructs a `SimpleDateFormat` using the given pattern and date format symbols.
  `SimpleDateFormat(String pattern, Locale locale)`
  Constructs a `SimpleDateFormat` using the given pattern and the default date format symbols for the given locale.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `applyLocalizedPattern(String pattern)`
  Applies the given localized pattern string to this date format.
  `void`
  `applyPattern(String pattern)`
  Applies the given pattern string to this date format.
  `Object`
  `clone()`
  Creates a copy of this `SimpleDateFormat`.
  `boolean`
  `equals(Object obj)`
  Compares the specified object with this `SimpleDateFormat` for equality.
  `StringBuffer`
  `format(Date date, StringBuffer toAppendTo, FieldPosition pos)`
  Formats the given `Date` into a date/time string and appends the result to the given `StringBuffer`.
  `AttributedCharacterIterator`
  `formatToCharacterIterator(Object obj)`
  Formats an Object producing an `AttributedCharacterIterator`.
  `Date`
  `get2DigitYearStart()`
  Returns the beginning date of the 100-year period 2-digit years are interpreted as being within.
  `DateFormatSymbols`
  `getDateFormatSymbols()`
  Gets a copy of the date and time format symbols of this date format.
  `int`
  `hashCode()`
  Returns the hash code value for this `SimpleDateFormat`.
  `Date`
  `parse(String text, ParsePosition pos)`
  Parses text from a string to produce a `Date`.
  `void`
  `set2DigitYearStart(Date startDate)`
  Sets the 100-year period 2-digit years will be interpreted as being in to begin on the date the user specifies.
  `void`
  `setDateFormatSymbols(DateFormatSymbols newFormatSymbols)`
  Sets the date and time format symbols of this date format.
  `String`
  `toLocalizedPattern()`
  Returns a localized pattern string describing this date format.
  `String`
  `toPattern()`
  Returns a pattern string describing this date format.
  `String`
  `toString()`
  Returns a string identifying this `SimpleDateFormat`, for debugging.

  ### Methods declared in class java.text.DateFormat

  `format, format, getAvailableLocales, getCalendar, getDateInstance, getDateInstance, getDateInstance, getDateTimeInstance, getDateTimeInstance, getDateTimeInstance, getInstance, getNumberFormat, getTimeInstance, getTimeInstance, getTimeInstance, getTimeZone, isLenient, parse, parseObject, setCalendar, setLenient, setNumberFormat, setTimeZone`

  ### Methods declared in class java.text.Format

  `format, parseObject`

  ### Methods declared in class java.lang.Object

  `finalize, getClass, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### SimpleDateFormat

    public SimpleDateFormat()
    Constructs a `SimpleDateFormat` using the default pattern and date format symbols for the default `FORMAT` locale. Note: This constructor may not support all locales. For full coverage, use the factory methods in the `DateFormat` class.

  - ### SimpleDateFormat

    public SimpleDateFormat(String pattern)
    Constructs a `SimpleDateFormat` using the given pattern and the default date format symbols for the default `FORMAT` locale. Note: This constructor may not support all locales. For full coverage, use the factory methods in the `DateFormat` class.

    This is equivalent to calling `SimpleDateFormat(pattern, Locale.getDefault(Locale.Category.FORMAT))`.

    Parameters:
      `pattern` - the pattern describing the date and time format
    Throws:
      `NullPointerException` - if the given pattern is null
      `IllegalArgumentException` - if the given pattern is invalid
    See Also:
      - `Locale.getDefault(java.util.Locale.Category)`
      - `Locale.Category.FORMAT`

  - ### SimpleDateFormat

    public SimpleDateFormat(String pattern, Locale locale)
    Constructs a `SimpleDateFormat` using the given pattern and the default date format symbols for the given locale. Note: This constructor may not support all locales. For full coverage, use the factory methods in the `DateFormat` class.
    Parameters:
      `pattern` - the pattern describing the date and time format
      `locale` - the locale whose date format symbols should be used
    Throws:
      `NullPointerException` - if the given pattern or locale is null
      `IllegalArgumentException` - if the given pattern is invalid

  - ### SimpleDateFormat

    public SimpleDateFormat(String pattern, DateFormatSymbols formatSymbols)
    Constructs a `SimpleDateFormat` using the given pattern and date format symbols.
    Parameters:
      `pattern` - the pattern describing the date and time format
      `formatSymbols` - the date format symbols to be used for formatting
    Throws:
      `NullPointerException` - if the given pattern or formatSymbols is null
      `IllegalArgumentException` - if the given pattern is invalid

- ## Method Details

  - ### set2DigitYearStart

    public void set2DigitYearStart(Date startDate)
    Sets the 100-year period 2-digit years will be interpreted as being in to begin on the date the user specifies.
    Parameters:
      `startDate` - During parsing, two digit years will be placed in the range `startDate` to `startDate + 100 years`.
    Throws:
      `NullPointerException` - if `startDate` is `null`.
    Since:
      1.2
    See Also:
      - `get2DigitYearStart()`

  - ### get2DigitYearStart

    public Date get2DigitYearStart()
    Returns the beginning date of the 100-year period 2-digit years are interpreted as being within.
    Returns:
      the start of the 100-year period into which two digit years are parsed
    Since:
      1.2
    See Also:
      - `set2DigitYearStart(java.util.Date)`

  - ### format

    public StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition pos)
    Formats the given `Date` into a date/time string and appends the result to the given `StringBuffer`.
    Specified by:
      `format` in class `DateFormat`
    Parameters:
      `date` - the date-time value to be formatted into a date-time string.
      `toAppendTo` - where the new date-time text is to be appended.
      `pos` - keeps track on the position of the field within the returned string. For example, given a date-time text `"1996.07.10 AD at 15:08:56 PDT"`, if the given `fieldPosition` is `DateFormat.YEAR_FIELD`, the begin index and end index of `fieldPosition` will be set to 0 and 4, respectively. Notice that if the same date-time field appears more than once in a pattern, the `fieldPosition` will be set for the first occurrence of that date-time field. For instance, formatting a `Date` to the date-time string `"1 PM PDT (Pacific Daylight Time)"` using the pattern `"h a z (zzzz)"` and the alignment field `DateFormat.TIMEZONE_FIELD`, the begin index and end index of `fieldPosition` will be set to 5 and 8, respectively, for the first occurrence of the timezone pattern character `'z'`.
    Returns:
      the formatted date-time string.
    Throws:
      `NullPointerException` - if any of the parameters is `null`.

  - ### formatToCharacterIterator

    public AttributedCharacterIterator formatToCharacterIterator(Object obj)
    Formats an Object producing an `AttributedCharacterIterator`. You can use the returned `AttributedCharacterIterator` to build the resulting String, as well as to determine information about the resulting String.

    Each attribute key of the AttributedCharacterIterator will be of type `DateFormat.Field`, with the corresponding attribute value being the same as the attribute key.

    Overrides:
      `formatToCharacterIterator` in class `Format`
    Parameters:
      `obj` - The object to format
    Returns:
      AttributedCharacterIterator describing the formatted value.
    Throws:
      `NullPointerException` - if obj is null.
      `IllegalArgumentException` - if the Format cannot format the given object, or if the Format's pattern string is invalid.
    Since:
      1.4

  - ### parse

    public Date parse(String text, ParsePosition pos)
    Parses text from a string to produce a `Date`.

    The method attempts to parse text starting at the index given by `pos`. If parsing succeeds, then the index of `pos` is updated to the index after the last character used (parsing does not necessarily use all characters up to the end of the string), and the parsed date is returned. The updated `pos` can be used to indicate the starting point for the next call to this method. If an error occurs, then the index of `pos` is not changed, the error index of `pos` is set to the index of the character where the error occurred, and null is returned.

    This parsing operation uses the `calendar` to produce a `Date`. All of the `calendar`'s date-time fields are cleared before parsing, and the `calendar`'s default values of the date-time fields are used for any missing date-time information. For example, the year value of the parsed `Date` is 1970 with `GregorianCalendar` if no year value is given from the parsing operation. The `TimeZone` value may be overwritten, depending on the given pattern and the time zone value in `text`. Any `TimeZone` value that has previously been set by a call to `setTimeZone` may need to be restored for further operations.

    Specified by:
      `parse` in class `DateFormat`
    Parameters:
      `text` - A `String`, part of which should be parsed.
      `pos` - A `ParsePosition` object with index and error index information as described above.
    Returns:
      A `Date` parsed from the string. In case of error, returns null.
    Throws:
      `NullPointerException` - if `text` or `pos` is null.

  - ### toPattern

    public String toPattern()
    Returns a pattern string describing this date format.
    Returns:
      a pattern string describing this date format.

  - ### toLocalizedPattern

    public String toLocalizedPattern()
    Returns a localized pattern string describing this date format.
    Returns:
      a localized pattern string describing this date format.

  - ### applyPattern

    public void applyPattern(String pattern)
    Applies the given pattern string to this date format.
    Parameters:
      `pattern` - the new date and time pattern for this date format
    Throws:
      `NullPointerException` - if the given pattern is null
      `IllegalArgumentException` - if the given pattern is invalid

  - ### applyLocalizedPattern

    public void applyLocalizedPattern(String pattern)
    Applies the given localized pattern string to this date format.
    Parameters:
      `pattern` - a String to be mapped to the new date and time format pattern for this format
    Throws:
      `NullPointerException` - if the given pattern is null
      `IllegalArgumentException` - if the given pattern is invalid

  - ### getDateFormatSymbols

    public DateFormatSymbols getDateFormatSymbols()
    Gets a copy of the date and time format symbols of this date format.
    Returns:
      the date and time format symbols of this date format
    See Also:
      - `setDateFormatSymbols(java.text.DateFormatSymbols)`

  - ### setDateFormatSymbols

    public void setDateFormatSymbols(DateFormatSymbols newFormatSymbols)
    Sets the date and time format symbols of this date format.
    Parameters:
      `newFormatSymbols` - the new date and time format symbols
    Throws:
      `NullPointerException` - if the given newFormatSymbols is null
    See Also:
      - `getDateFormatSymbols()`

  - ### clone

    public Object clone()
    Creates a copy of this `SimpleDateFormat`. This also clones the format's date format symbols.
    Overrides:
      `clone` in class `DateFormat`
    Returns:
      a clone of this `SimpleDateFormat`
    See Also:
      - `Cloneable`

  - ### hashCode

    public int hashCode()
    Returns the hash code value for this `SimpleDateFormat`.
    Overrides:
      `hashCode` in class `DateFormat`
    Implementation Requirements:
      This method calculates the hash code value using the value returned by `toPattern()`.
    Returns:
      the hash code value for this `SimpleDateFormat`
    See Also:
      - `Object.hashCode()`

  - ### toString

    public String toString()
    Returns a string identifying this `SimpleDateFormat`, for debugging.
    Overrides:
      `toString` in class `Object`
    Returns:
      a string identifying this `SimpleDateFormat`, for debugging

  - ### equals

    public boolean equals(Object obj)
    Compares the specified object with this `SimpleDateFormat` for equality. Returns true if the object is also a `SimpleDateFormat` and the two formats would format any value the same.
    Overrides:
      `equals` in class `DateFormat`
    Implementation Requirements:
      This method performs an equality check with a notion of class identity based on `getClass()`, rather than `instanceof`. Therefore, in the equals methods in subclasses, no instance of this class should compare as equal to an instance of a subclass.
    Parameters:
      `obj` - object to be compared for equality
    Returns:
      `true` if the specified object is equal to this `SimpleDateFormat`
    See Also:
      - `Object.equals(Object)`