Customizing Formats
Version note: This Date and Time section uses the date and time APIs in the java.util package. The java.time APIs, available in the JDK 8 release, provides a comprehensive date and time model that offers significant improvements over the java.util classes. The java.time APIs are described in the Date Time trail. The Legacy Date-Time Code page might be of particular interest.
The previous section, Using Predefined Formats, described the formatting styles provided by the DateFormat class. In most cases these predefined formats are adequate. However, if you want to create your own customized formats, you can use the SimpleDateFormat class.
The code examples that follow demonstrate the methods of the SimpleDateFormat class. You can find the full source code for the examples in the file named SimpleDateFormatDemo .
About Patterns
When you create a SimpleDateFormat object, you specify a pattern String . The contents of the pattern String determine the format of the date and time. For a full description of the pattern’s syntax, see the tables in Date Format Pattern Syntax.
The following code formats a date and time according to the pattern String passed to the SimpleDateFormat constructor. The String returned by the format method contains the formatted date and time that are to be displayed.
Date today; String output; SimpleDateFormat formatter; formatter = new SimpleDateFormat(pattern, currentLocale); today = new Date(); output = formatter.format(today); System.out.println(pattern + " " + output);
The following table shows the output generated by the previous code example when the U.S. Locale is specified:
| Pattern | Output |
|---|---|
| dd.MM.yy | 30.06.09 |
| yyyy.MM.dd G ‘at’ hh:mm:ss z | 2009.06.30 AD at 08:29:36 PDT |
| EEE, MMM d, »yy | Tue, Jun 30, ’09 |
| h:mm a | 8:29 PM |
| H:mm | 8:29 |
| H:mm:ss:SSS | 8:28:36:249 |
| K:mm a,z | 8:29 AM,PDT |
| yyyy.MMMMM.dd GGG hh:mm aaa | 2009.June.30 AD 08:29 AM |
Patterns and Locale
The SimpleDateFormat class is locale-sensitive. If you instantiate SimpleDateFormat without a Locale parameter, it will format the date and time according to the default Locale . Both the pattern and the Locale determine the format. For the same pattern, SimpleDateFormat may format a date and time differently if the Locale varies.
In the example code that follows, the pattern is hardcoded in the statement that creates the SimpleDateFormat object:
Date today; String result; SimpleDateFormat formatter; formatter = new SimpleDateFormat("EEE d MMM yy", currentLocale); today = new Date(); result = formatter.format(today); System.out.println("Locale: " + currentLocale.toString()); System.out.println("Result: " + result); When the currentLocale is set to different values, the preceding code example generates this output:
Locale: fr_FR Result: mar. 30 juin 09 Locale: de_DE Result: Di 30 Jun 09 Locale: en_US Result: Tue 30 Jun 09
Date Format Pattern Syntax
You can design your own format patterns for dates and times from the list of symbols in the following table:
| Symbol | Meaning | Presentation | Example |
|---|---|---|---|
| G | era designator | Text | AD |
| y | year | Number | 2009 |
| M | month in year | Text & Number | July & 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 | millisecond | Number | 978 |
| E | day in week | Text | Tuesday |
| D | day in year | Number | 189 |
| F | day of week in month | Number | 2 (2nd Wed in July) |
| w | week in year | Number | 27 |
| W | week in month | Number | 2 |
| 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 |
| ‘ | escape for text | Delimiter | (none) |
| ‘ | single quote | Literal | ‘ |
Characters that are not letters are treated as quoted text. That is, they will appear in the formatted text even if they are not enclosed within single quotes.
The number of symbol letters you specify also determines the format. For example, if the «zz» pattern results in «PDT,» then the «zzzz» pattern generates «Pacific Daylight Time.» The following table summarizes these rules:
| Presentation | Number of Symbols | Result |
|---|---|---|
| Text | 1 — 3 | abbreviated form, if one exists |
| Text | >= 4 | full form |
| Number | minimum number of digits is required | shorter numbers are padded with zeros (for a year, if the count of ‘y’ is 2, then the year is truncated to 2 digits) |
| Text & Number | 1 — 2 | number form |
| Text & Number | 3 | text form |
Class SimpleDateFormat
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
- 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.
- 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.
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() .
- 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.
GMTOffsetTimeZone:GMTSign Hours:Minutes Sign: one of+ -Hours: Digit Digit Digit Minutes: Digit Digit Digit: one of0 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.
RFC822TimeZone: Sign TwoDigitHours Minutes TwoDigitHours: Digit Digit
ISO8601TimeZone: OneLetterISO8601TimeZone TwoLetterISO8601TimeZone ThreeLetterISO8601TimeZone OneLetterISO8601TimeZone: Sign TwoDigitHoursZTwoLetterISO8601TimeZone: Sign TwoDigitHours MinutesZThreeLetterISO8601TimeZone: Sign TwoDigitHours:MinutesZ
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.