public 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, all unquoted ASCII letters [A-Za-z] are reserved as pattern letters representing calendar fields. SimpleDateFormat supports the date and time formatting algorithm and pattern letters defined by UTS#35 Unicode Locale Data Markup Language (LDML). The following pattern letters are currently available (note that the actual values depend on CLDR and may change from the examples shown here):

Field	Sym.	No.	Example	Description
era	G	1..3	AD	Era - Replaced with the Era string for the current date. One to three letters for the abbreviated form, four letters for the long (wide) form, five for the narrow form.
		4	Anno Domini
		5	A
year	y	1..n	1996	Year. Normally the length specifies the padding, but for two letters it also specifies the maximum length. Example: Year y yy yyy yyyy yyyyy AD 1 1 01 001 0001 00001 AD 12 12 12 012 0012 00012 AD 123 123 23 123 0123 00123 AD 1234 1234 34 1234 1234 01234 AD 12345 12345 45 12345 12345 12345
	Y	1..n	1997	Year (in "Week of Year" based calendars). Normally the length specifies the padding, but for two letters it also specifies the maximum length. This year designation is used in ISO year-week calendar as defined by ISO 8601, but can be used in non-Gregorian based calendar systems where week date processing is desired. May not always be the same value as calendar year.
	u	1..n	4601	Extended year. This is a single number designating the year of this calendar system, encompassing all supra-year fields. For example, for the Julian calendar system, year numbers are positive, with an era of BCE or CE. An extended year value for the Julian calendar system assigns positive values to CE years and negative values to BCE years, with 1 BCE being year 0.
	U	1..3	甲子	Cyclic year name. Calendars such as the Chinese lunar calendar (and related calendars) and the Hindu calendars use 60-year cycles of year names. Use one through three letters for the abbreviated name, four for the full (wide) name, or five for the narrow name (currently the data only provides abbreviated names, which will be used for all requested name widths). If the calendar does not provide cyclic year name data, or if the year value to be formatted is out of the range of years for which cyclic name data is provided, then numeric formatting is used (behaves like 'y').
		4	(currently also 甲子)
		5	(currently also 甲子)
quarter	Q	1..2	02	Quarter - Use one or two for the numerical quarter, three for the abbreviation, or four for the full (wide) name (five for the narrow name is not yet supported).
		3	Q2
		4	2nd quarter
	q	1..2	02	Stand-Alone Quarter - Use one or two for the numerical quarter, three for the abbreviation, or four for the full name (five for the narrow name is not yet supported).
		3	Q2
		4	2nd quarter
month	M	1..2	09	Month - Use one or two for the numerical month, three for the abbreviation, four for the full (wide) name, or five for the narrow name. With two ("MM"), the month number is zero-padded if necessary (e.g. "08").
		3	Sep
		4	September
		5	S
	L	1..2	09	Stand-Alone Month - Use one or two for the numerical month, three for the abbreviation, four for the full (wide) name, or 5 for the narrow name. With two ("LL"), the month number is zero-padded if necessary (e.g. "08").
		3	Sep
		4	September
		5	S
week	w	1..2	27	Week of Year. Use "w" to show the minimum number of digits, or "ww" to always show two digits (zero-padding if necessary, e.g. "08").
	W	1	3	Week of Month
day	d	1..2	1	Date - Day of the month. Use "d" to show the minimum number of digits, or "dd" to always show two digits (zero-padding if necessary, e.g. "08").
	D	1..3	345	Day of year
	F	1	2	Day of Week in Month. The example is for the 2nd Wed in July
	g	1..n	2451334	Modified Julian day. This is different from the conventional Julian day number in two regards. First, it demarcates days at local zone midnight, rather than noon GMT. Second, it is a local number; that is, it depends on the local time zone. It can be thought of as a single number that encompasses all the date-related fields.
week day	E	1..3	Tue	Day of week - Use one through three letters for the short day, four for the full (wide) name, five for the narrow name, or six for the short name.
		4	Tuesday
		5	T
		6	Tu
	e	1..2	2	Local day of week. Same as E except adds a numeric value that will depend on the local starting day of the week, using one or two letters. For this example, Monday is the first day of the week.
		3	Tue
		4	Tuesday
		5	T
		6	Tu
	c	1	2	Stand-Alone local day of week - Use one letter for the local numeric value (same as 'e'), three for the short day, four for the full (wide) name, five for the narrow name, or six for the short name.
		3	Tue
		4	Tuesday
		5	T
		6	Tu
period	a	1	AM	AM or PM
hour	h	1..2	11	Hour [1-12]. When used in skeleton data or in a skeleton passed in an API for flexible data pattern generation, it should match the 12-hour-cycle format preferred by the locale (h or K); it should not match a 24-hour-cycle format (H or k). Use hh for zero padding.
	H	1..2	13	Hour [0-23]. When used in skeleton data or in a skeleton passed in an API for flexible data pattern generation, it should match the 24-hour-cycle format preferred by the locale (H or k); it should not match a 12-hour-cycle format (h or K). Use HH for zero padding.
	K	1..2	0	Hour [0-11]. When used in a skeleton, only matches K or h, see above. Use KK for zero padding.
	k	1..2	24	Hour [1-24]. When used in a skeleton, only matches k or H, see above. Use kk for zero padding.
minute	m	1..2	59	Minute. Use "m" to show the minimum number of digits, or "mm" to always show two digits (zero-padding if necessary, e.g. "08")..
second	s	1..2	12	Second. Use "s" to show the minimum number of digits, or "ss" to always show two digits (zero-padding if necessary, e.g. "08").
	S	1..n	3450	Fractional Second - truncates (like other time fields) to the count of letters when formatting. Appends zeros if more than 3 letters specified. Truncates at three significant digits when parsing. (example shows display using pattern SSSS for seconds value 12.34567)
	A	1..n	69540000	Milliseconds in day. This field behaves exactly like a composite of all time-related fields, not including the zone fields. As such, it also reflects discontinuities of those fields on DST transition days. On a day of DST onset, it will jump forward. On a day of DST cessation, it will jump backward. This reflects the fact that is must be combined with the offset field to obtain a unique local time value.
zone	z	1..3	PDT	The short specific non-location format. Where that is unavailable, falls back to the short localized GMT format ("O").
		4	Pacific Daylight Time	The long specific non-location format. Where that is unavailable, falls back to the long localized GMT format ("OOOO").
	Z	1..3	-0800	The ISO8601 basic format with hours, minutes and optional seconds fields. The format is equivalent to RFC 822 zone format (when optional seconds field is absent). This is equivalent to the "xxxx" specifier.
		4	GMT-8:00	The long localized GMT format. This is equivalent to the "OOOO" specifier.
		5	-08:00 -07:52:58	The ISO8601 extended format with hours, minutes and optional seconds fields. The ISO8601 UTC indicator "Z" is used when local time offset is 0. This is equivalent to the "XXXXX" specifier.
	O	1	GMT-8	The short localized GMT format.
		4	GMT-08:00	The long localized GMT format.
	v	1	PT	The short generic non-location format. Where that is unavailable, falls back to the generic location format ("VVVV"), then the short localized GMT format as the final fallback.
		4	Pacific Time	The long generic non-location format. Where that is unavailable, falls back to generic location format ("VVVV").
	V	1	uslax	The short time zone ID. Where that is unavailable, the special short time zone ID unk (Unknown Zone) is used. Note: This specifier was originally used for a variant of the short specific non-location format, but it was deprecated in the later version of the LDML specification. In CLDR 23/ICU 51, the definition of the specifier was changed to designate a short time zone ID.
		2	America/Los_Angeles	The long time zone ID.
		3	Los Angeles	The exemplar city (location) for the time zone. Where that is unavailable, the localized exemplar city name for the special zone Etc/Unknown is used as the fallback (for example, "Unknown City").
		4	Los Angeles Time	The generic location format. Where that is unavailable, falls back to the long localized GMT format ("OOOO"; Note: Fallback is only necessary with a GMT-style Time Zone ID, like Etc/GMT-830.) This is especially useful when presenting possible timezone choices for user selection, since the naming is more uniform than the "v" format.
	X	1	-08 +0530 Z	The ISO8601 basic format with hours field and optional minutes field. The ISO8601 UTC indicator "Z" is used when local time offset is 0.
		2	-0800 Z	The ISO8601 basic format with hours and minutes fields. The ISO8601 UTC indicator "Z" is used when local time offset is 0.
		3	-08:00 Z	The ISO8601 extended format with hours and minutes fields. The ISO8601 UTC indicator "Z" is used when local time offset is 0.
		4	-0800 -075258 Z	The ISO8601 basic format with hours, minutes and optional seconds fields. (Note: The seconds field is not supported by the ISO8601 specification.) The ISO8601 UTC indicator "Z" is used when local time offset is 0.
		5	-08:00 -07:52:58 Z	The ISO8601 extended format with hours, minutes and optional seconds fields. (Note: The seconds field is not supported by the ISO8601 specification.) The ISO8601 UTC indicator "Z" is used when local time offset is 0.
	x	1	-08 +0530	The ISO8601 basic format with hours field and optional minutes field.
		2	-0800	The ISO8601 basic format with hours and minutes fields.
		3	-08:00	The ISO8601 extended format with hours and minutes fields.
		4	-0800 -075258	The ISO8601 basic format with hours, minutes and optional seconds fields. (Note: The seconds field is not supported by the ISO8601 specification.)
		5	-08:00 -07:52:58	The ISO8601 extended format with hours, minutes and optional seconds fields. (Note: The seconds field is not supported by the ISO8601 specification.)

Any characters in the pattern that are not in the ranges of ['a'..'z'] and ['A'..'Z'] will be treated as quoted text. For instance, characters like ':', '.', ' ', '#' and '@' will appear in the resulting time text even they are not embraced within single quotes.

A pattern containing any invalid pattern letter will result in a thrown exception during formatting or parsing.

Examples Using the US Locale:

Format Pattern                         Result
--------------                         -------
"yyyy.MM.dd G 'at' HH:mm:ss vvvv" ->>  1996.07.10 AD at 15:08:56 Pacific Time
"EEE, MMM d, ''yy"                ->>  Wed, July 10, '96
"h:mm a"                          ->>  12:08 PM
"hh 'o''clock' a, zzzz"           ->>  12 o'clock PM, Pacific Daylight Time
"K:mm a, vvv"                     ->>  0:00 PM, PT
"yyyyy.MMMMM.dd GGG hh:mm aaa"    ->>  01996.July.10 AD 12:08 PM

SimpleTimeZone pdt = new SimpleTimeZone(-8 * 60 * 60 * 1000, "PST");
pdt.setStartRule(Calendar.APRIL, 1, Calendar.SUNDAY, 2*60*60*1000);
pdt.setEndRule(Calendar.OCTOBER, -1, Calendar.SUNDAY, 2*60*60*1000);


// Format the current time.
SimpleDateFormat formatter
    = new SimpleDateFormat ("yyyy.MM.dd G 'at' hh:mm:ss a zzz");
Date currentTime_1 = new Date();
String dateString = formatter.format(currentTime_1);


// Parse the previous string back into a Date.
ParsePosition pos = new ParsePosition(0);
Date currentTime_2 = formatter.parse(dateString, pos);

When parsing a date string using the abbreviated year pattern ("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 com.ibm.icu.lang.UCharacter#isDigit(int), 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 the year pattern does not have exactly two 'y' characters, 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.

When numeric fields abut one another directly, with no intervening delimiter characters, they constitute a run of abutting numeric fields. Such runs are parsed specially. For example, the format "HHmmss" parses the input text "123456" to 12:34:56, parses the input text "12345" to 1:23:45, and fails to parse "1234". In other words, the leftmost field of the run is flexible, while the others keep a fixed width. If the parse fails anywhere in the run, then the leftmost field is shortened by one character, and the entire run is parsed again. This is repeated until either the parse succeeds or the leftmost field is one character in length. If the parse still fails at that point, the parse of the run fails.

For time zones that have no names, use strings GMT+hours:minutes or GMT-hours:minutes.

The calendar defines what is the first day of the week, the first week of the year, whether hours are zero based or not (0 vs 12 or 24), and the time zone. There is one common decimal format to handle all the numbers; the digit count is handled programmatically according to the pattern.

Synchronization