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):
Pattern letters are usually repeated, as their number determines the exact presentation:
Letter Date or Time Component Presentation Examples GEra designator Text ADyYear Year 1996;96YWeek year Year 2009;09MMonth in year Month July;Jul;07wWeek in year Number 27WWeek in month Number 2DDay in year Number 189dDay in month Number 10FDay of week in month Number 2EDay name in week Text Tuesday;TueuDay number of week (1 = Monday, …, 7 = Sunday) Number 1aAm/pm marker Text PMHHour in day (0-23) Number 0kHour in day (1-24) Number 24KHour in am/pm (0-11) Number 0hHour in am/pm (1-12) Number 12mMinute in hour Number 30sSecond in minute Number 55SMillisecond Number 978zTime zone General time zone Pacific Standard Time;PST;GMT-08:00ZTime zone RFC 822 time zone -0800XTime 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.
- 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
Calendaris 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”),
SimpleDateFormatmust 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 theSimpleDateFormatinstance is created. For example, using a pattern of “MM/dd/yy” and aSimpleDateFormatinstance 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 byCharacter.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 togetCalendar().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.
- 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:
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.GMTSign Hours:Minutes Sign: one of+ -Hours: Digit Digit Digit Minutes: Digit Digit Digit: one of0 1 2 3 4 5 6 7 8 9For 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 DigitTwoDigitHours 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 TwoDigitHoursOther definitions are as for general time zones or RFC 822 time zones.ZTwoLetterISO8601TimeZone: Sign TwoDigitHours MinutesZThreeLetterISO8601TimeZone: Sign TwoDigitHours:MinutesZFor 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,
IllegalArgumentExceptionis thrown when constructing aSimpleDateFormator 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.
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
Example Code
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;
public class Main {
public static void main(String[] args) {
String gmt_pattern = "EEE, d MMM yyyy HH:mm:ss z";
String cst_pattern = "EEE MMM d HH:mm:ss 'CST' yyyy";
String pattern = "yyyy-MM-dd HH:mm:ss";
SimpleDateFormat sdf = null;
sdf = new SimpleDateFormat();
sdf.applyPattern(gmt_pattern);
sdf.setTimeZone(TimeZone.getTimeZone("GMT+8"));
System.out.println("當前時間轉GMT+時區－中文 => " + sdf.format(new Date()));
sdf = new SimpleDateFormat(gmt_pattern, Locale.US);
sdf.setTimeZone(TimeZone.getTimeZone("GMT"));
System.out.println("當前時間轉GMT－英文 => " + sdf.format(new Date()));
try {
sdf = new SimpleDateFormat(gmt_pattern, Locale.US);
sdf.setTimeZone(TimeZone.getTimeZone("GMT+8"));
String gmtTime = "Tue, 18 Jul 2017 07:10:29 GMT";
System.out.println("GMT轉東八區時間CST =〉" + sdf.parse(gmtTime));
String cstTime = "Tue Jul 18 15:10:29 CST 2017";
sdf = new SimpleDateFormat(cst_pattern, Locale.US);
Date date = sdf.parse(cstTime);
sdf.applyPattern(pattern);
System.out.println("CST時間轉自定義格式 =〉" + sdf.format(date));
} catch (ParseException e) {
e.printStackTrace();
}
}
}
// 打印日誌
當前時間轉GMT+時區－中文 => 星期二, 18 七月 2017 15:20:42 GMT+08:00
當前時間轉GMT－英文 => Tue, 18 Jul 2017 07:20:42 GMT
GMT轉東八區時間CST =〉Tue Jul 18 15:10:29 CST 2017
CST時間轉自定義格式 =〉2017-07-18 15:10:29