← 返回首页
SimpleDateFormat (Java SE 26 & JDK 26)
JavaScript is disabled on your browser.
  1. java.base
  2. java.text
  3. SimpleDateFormat
Contents  
  1. Description
    1. Date and Time Patterns
      1. Examples
      2. Synchronization
  2. Nested Class Summary
  3. Field Summary
  4. Constructor Summary
  5. Method Summary
    1. Methods declared in class DateFormat
    2. Methods declared in class Format
    3. Methods declared in class Object
  6. Constructor Details
    1. SimpleDateFormat()
    2. SimpleDateFormat(String)
    3. SimpleDateFormat(String, Locale)
    4. SimpleDateFormat(String, DateFormatSymbols)
  7. Method Details
    1. set2DigitYearStart(Date)
    2. get2DigitYearStart()
    3. format(Date, StringBuffer, FieldPosition)
    4. formatToCharacterIterator(Object)
    5. parse(String, ParsePosition)
    6. toPattern()
    7. toLocalizedPattern()
    8. applyPattern(String)
    9. applyLocalizedPattern(String)
    10. getDateFormatSymbols()
    11. setDateFormatSymbols(DateFormatSymbols)
    12. clone()
    13. hashCode()
    14. toString()
    15. equals(Object)
Hide sidebar  Show sidebar

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' not in the table below are reserved). applyPattern(String), applyLocalizedPattern(String), and the SimpleDateFormat constructors throw IllegalArgumentException when passed a pattern containing an unquoted reserved character.

Chart shows pattern letters, date/time component, presentation, and examples. Letter Date or Time Component Presentation Examples G y Y M L w W D d F E u a H k K h m s S z Z X
Era designator Text AD
Year Year 1996; 96
Week year Year 2009; 09
Month in year (context sensitive) Month July; Jul; 07
Month in year (standalone form) Month July; Jul; 07
Week in year Number 27
Week in month Number 2
Day in year Number 189
Day in month Number 10
Day of week in month Number 2
Day name in week Text Tuesday; Tue
Day number of week (1 = Monday, ..., 7 = Sunday) Number 1
Am/pm marker Text PM
Hour in day (0-23) Number 0
Hour in day (1-24) Number 24
Hour in am/pm (0-11) Number 0
Hour in am/pm (1-12) Number 12
Minute in hour Number 30
Second in minute Number 55
Millisecond Number 978
Time zone General time zone Pacific Standard Time; PST; GMT-08:00
Time zone RFC 822 time zone -0800
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" "EEE, MMM d, ''yy" "h:mm a" "hh 'o''clock' a, zzzz" "K:mm a, z" "yyyyy.MMMMM.dd GGG hh:mm aaa" "EEE, d MMM yyyy HH:mm:ss Z" "yyMMddHHmmssZ" "yyyy-MM-dd'T'HH:mm:ss.SSSZ" "yyyy-MM-dd'T'HH:mm:ss.SSSXXX" "YYYY-'W'ww-u"
2001.07.04 AD at 12:08:56 PDT
Wed, Jul 4, '01
12:08 PM
12 o'clock PM, Pacific Daylight Time
0:08 PM, PDT
02001.July.04 AD 12:08 PM
Wed, 4 Jul 2001 12:08:56 -0700
010704120856-0700
2001-07-04T12:08:56.235-0700
2001-07-04T12:08:56.235-07:00
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:

Report a bug or suggest an enhancement
For further API reference and developer documentation see the Java SE Documentation, which contains more detailed, developer-targeted descriptions with conceptual overviews, definitions of terms, workarounds, and working code examples. Other versions.
Java is a trademark or registered trademark of Oracle and/or its affiliates in the US and other countries.
Copyright © 1993, 2026, Oracle and/or its affiliates, 500 Oracle Parkway, Redwood Shores, CA 94065 USA.
All rights reserved. Use is subject to license terms and the documentation redistribution policy.

Scripting on this page tracks web page traffic, but does not change the content in any way.