Chronoscope

Patterns

Symbol Meaning Presentation Example
G era designator Text AD
y year Number 1996
M month in year Text or Number July (or) 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 fractional second Number 978
E day of week Text Tuesday
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
Z time zone (RFC 822) Number -0800
v time zone (generic) Text Pacific Time
' escape for text Delimiter 'Date='
'' single quote Literal 'o''clock'

The number of pattern letters influences the format, as follows:

Text
if 4 or more, then use the full form; if less than 4, use short or abbreviated form if it exists (e.g., "EEEE" produces "Monday", "EEE" produces "Mon")
Number
the minimum number of digits. Shorter numbers are zero-padded to this amount (e.g. if "m" produces "6", "mm" produces "06"). Year is handled specially; that is, if the count of 'y' is 2, the Year will be truncated to 2 digits. (e.g., if "yyyy" produces "1997", "yy" produces "97".) Unlike other fields, fractional seconds are padded on the right with zero.
Text or Number
3 or more, use text, otherwise use number. (e.g. "M" produces "1", "MM" produces "01", "MMM" produces "Jan", and "MMMM" produces "January".

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 ':', '.', ' ' (space), '#' and '@' will appear in the resulting time text even they are not embraced within single quotes.

Parsing Dates and Times

This implementation could parse partial date/time. Current date will be used to fill in the unavailable date part. 00:00:00 will be used to fill in the time part.

As with formatting (described above), the count of pattern letters determine the parsing behavior.

Text
4 or more pattern letters--use full form, less than 4--use short or abbreviated form if one exists. In parsing, we will always try long format, then short.
Number
the minimum number of digits.
Text or Number
3 or more characters means use text, otherwise use number

Although the current pattern specification doesn't not specify behavior for all letters, it may in the future. It is strongly discouraged to used unspecified letters as literal text without being surrounded by quotes.

Examples

Pattern Formatted Text
"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

Additional Parsing Considerations

When parsing a date string using the abbreviated year pattern ("yy"), the parser 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 parser instance is created. For example, using a pattern of "MM/dd/yy" and a DateTimeFormat object 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. If the year pattern does not have exactly two 'y' characters, the year is interpreted literally, regardless of the number of digits. For example, 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.

In the current implementation, timezone parsing only supports GMT:hhmm, GMT:+hhmm, and GMT:-hhmm.

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