DateIntervalFormat is a class for formatting and parsing date intervals in a language-independent manner. More...
DateIntervalFormat is a class for formatting and parsing date intervals in a language-independent manner.
Only formatting is supported, parsing is not supported.
Date interval means from one date to another date, for example, from "Jan 11, 2008" to "Jan 18, 2008". We introduced class DateInterval to represent it. DateInterval is a pair of UDate, which is the standard milliseconds since 24:00 GMT, Jan 1, 1970.
DateIntervalFormat formats a DateInterval into text as compactly as possible. For example, the date interval format from "Jan 11, 2008" to "Jan 18,. 2008" is "Jan 11-18, 2008" for English. And it parses text into DateInterval, although initially, parsing is not supported.
There is no structural information in date time patterns. For any punctuations and string literals inside a date time pattern, we do not know whether it is just a separator, or a prefix, or a suffix. Without such information, so, it is difficult to generate a sub-pattern (or super-pattern) by algorithm. So, formatting a DateInterval is pattern-driven. It is very similar to formatting in SimpleDateFormat. We introduce class DateIntervalInfo to save date interval patterns, similar to date time pattern in SimpleDateFormat.
Logically, the interval patterns are mappings from (skeleton, the_largest_different_calendar_field) to (date_interval_pattern).
A skeleton
For those non-digit calendar fields, the pattern letter length is important, such as MMM, MMMM, and MMMMM; EEE and EEEE, and the field's pattern letter length is honored.
For the digit calendar fields, such as M or MM, d or dd, yy or yyyy, the field pattern length is ignored and the best match, which is defined in date time patterns, will be returned without honor the field pattern letter length in skeleton.
The calendar fields we support for interval formatting are: year, month, date, day-of-week, am-pm, hour, hour-of-day, minute, second, and millisecond. (though we do not currently have specific intervalFormat date for skeletons with seconds and millisecond). Those calendar fields can be defined in the following order: year > month > date > hour (in day) > minute > second > millisecond
The largest different calendar fields between 2 calendars is the first different calendar field in above order.
For example: the largest different calendar fields between "Jan 10, 2007" and "Feb 20, 2008" is year.
For other calendar fields, the compact interval formatting is not supported. And the interval format will be fall back to fall-back patterns, which is mostly "{date0} - {date1}".
There is a set of pre-defined static skeleton strings. There are pre-defined interval patterns for those pre-defined skeletons in locales' resource files. For example, for a skeleton UDAT_YEAR_ABBR_MONTH_DAY, which is "yMMMd", in en_US, if the largest different calendar field between date1 and date2 is "year", the date interval pattern is "MMM d, yyyy - MMM d, yyyy", such as "Jan 10, 2007 - Jan 10, 2008". If the largest different calendar field between date1 and date2 is "month", the date interval pattern is "MMM d - MMM d, yyyy", such as "Jan 10 - Feb 10, 2007". If the largest different calendar field between date1 and date2 is "day", the date interval pattern is "MMM d-d, yyyy", such as "Jan 10-20, 2007".
For date skeleton, the interval patterns when year, or month, or date is different are defined in resource files. For time skeleton, the interval patterns when am/pm, or hour, or minute is different are defined in resource files.
If a skeleton is not found in a locale's DateIntervalInfo, which means the interval patterns for the skeleton is not defined in resource file, the interval pattern will falls back to the interval "fallback" pattern defined in resource file. If the interval "fallback" pattern is not defined, the default fall-back is "{date0} - {data1}".
For the combination of date and time, The rule to generate interval patterns are:
If two dates are the same, the interval pattern is the single date pattern. For example, interval pattern from "Jan 10, 2007" to "Jan 10, 2007" is "Jan 10, 2007".
Or if the presenting fields between 2 dates have the exact same values, the interval pattern is the single date pattern. For example, if user only requests year and month, the interval pattern from "Jan 10, 2007" to "Jan 20, 2007" is "Jan 2007".
DateIntervalFormat needs the following information for correct formatting: time zone, calendar type, pattern, date format symbols, and date interval patterns. It can be instantiated in 2 ways:
For the calendar field pattern letter, such as G, y, M, d, a, h, H, m, s etc. DateIntervalFormat uses the same syntax as that of DateTime format.
Code Sample: general usage
DateInterval* dtInterval = new DateInterval(1000*3600*24, 1000*3600*24*2);
Locale("en", "GB", ""), status);
UnicodeUnicodeString dateIntervalString;
FieldPosition pos = 0;
dtIntervalFmt->format(dtInterval, dateIntervalUnicodeString, pos, status);
delete dtIntervalFmt;
static DateIntervalFormat * createInstance(const UnicodeString &skeleton, UErrorCode &status)
Construct a DateIntervalFormat from skeleton and the default locale.
DateIntervalFormat(const DateIntervalFormat &)
Copy constructor.
#define UDAT_YEAR_MONTH_DAY
Constant for date skeleton with year, month, and day.
UErrorCode
Standard ICU4C error code type, a substitute for exceptions.
@ U_ZERO_ERROR
No error, no warning.
Definition at line 300 of file dtitvfmt.h.
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