DateIntervalFormat

public class DateIntervalFormat
extends UFormat

java.lang.Object
   ↳ java.text.Format
     ↳ android.icu.text.UFormat
       ↳ android.icu.text.DateIntervalFormat

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

  1. only keeps the field pattern letter and ignores all other parts in a pattern, such as space, punctuations, and string literals.
  2. hides the order of fields.
  3. might hide a field's pattern letter length. 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