Using Predefined 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 DateFormat class allows you to format dates and times with predefined styles in a locale-sensitive manner. The sections that follow demonstrate how to use the DateFormat class with a program called DateFormatDemo.java .
Dates
Formatting dates with the DateFormat class is a two-step process. First, you create a formatter with the getDateInstance method. Second, you invoke the format method, which returns a String containing the formatted date. The following example formats today’s date by calling these two methods:
Date today; String dateOut; DateFormat dateFormatter; dateFormatter = DateFormat.getDateInstance(DateFormat.DEFAULT, currentLocale); today = new Date(); dateOut = dateFormatter.format(today); System.out.println(dateOut + " " + currentLocale.toString());
The output generated by this code follows. Notice that the formats of the dates vary with Locale . Since DateFormat is locale-sensitive, it takes care of the formatting details for each Locale .
30 juin 2009 fr_FR 30.06.2009 de_DE Jun 30, 2009 en_US
The preceding code example specified the DEFAULT formatting style. The DEFAULT style is just one of the predefined formatting styles that the DateFormat class provides, as follows:
The following table shows how dates are formatted for each style with the U.S. and French locales:
| Style | U.S. Locale | French Locale |
|---|---|---|
| DEFAULT | Jun 30, 2009 | 30 juin 2009 |
| SHORT | 6/30/09 | 30/06/09 |
| MEDIUM | Jun 30, 2009 | 30 juin 2009 |
| LONG | June 30, 2009 | 30 juin 2009 |
| FULL | Tuesday, June 30, 2009 | mardi 30 juin 2009 |
Times
Date objects represent both dates and times. Formatting times with the DateFormat class is similar to formatting dates, except that you create the formatter with the getTimeInstance method, as follows:
DateFormat timeFormatter = DateFormat.getTimeInstance(DateFormat.DEFAULT, currentLocale);
The table that follows shows the various predefined format styles for the U.S. and German locales:
| Style | U.S. Locale | German Locale |
|---|---|---|
| DEFAULT | 7:03:47 AM | 7:03:47 |
| SHORT | 7:03 AM | 07:03 |
| MEDIUM | 7:03:47 AM | 07:03:07 |
| LONG | 7:03:47 AM PDT | 07:03:45 PDT |
| FULL | 7:03:47 AM PDT | 7.03 Uhr PDT |
Both Dates and Times
To display a date and time in the same String , create the formatter with the getDateTimeInstance method. The first parameter is the date style, and the second is the time style. The third parameter is the Locale . Here’s a quick example:
DateFormat formatter = DateFormat.getDateTimeInstance( DateFormat.LONG, DateFormat.LONG, currentLocale);
The following table shows the date and time formatting styles for the U.S. and French locales:
| Style | U.S. Locale | French Locale |
|---|---|---|
| DEFAULT | Jun 30, 2009 7:03:47 AM | 30 juin 2009 07:03:47 |
| SHORT | 6/30/09 7:03 AM | 30/06/09 07:03 |
| MEDIUM | Jun 30, 2009 7:03:47 AM | 30 juin 2009 07:03:47 |
| LONG | June 30, 2009 7:03:47 AM PDT | 30 juin 2009 07:03:47 PDT |
| FULL | Tuesday, June 30, 2009 7:03:47 AM PDT | mardi 30 juin 2009 07 h 03 PDT |
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.