Re: Proposal: Clarification of DateFormat 'S' field

On further thought, I think the 'S' field should implement half-up 
rounding.

[Alan S Liu/San Jose/IBM@IBMUS; [email protected];; IBM Globalization; 
5600 Cottle Road; San Jose, CA 95193;; (408) 256-3155]

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Proposal:  Change semantics of 'S' from "milliseconds" to "fractions of a 
second."

This will make the 'S' field more generally useful in patterns such as 
"hh:mm:ss.S" immediately, and will allow for any future changes in which 
time representation is changed from having millisecond resolution.

Currently the 'S' field in DateFormat is defined to display milliseconds. 
I would like to change this definition so that it displays fractions of a 
second.  That is, given the time 1:30:01.234567891, or 234,567,981 ns 
after 1:30:01, the following format behavior is proposed:

ss.S => 01.2
ss.SS => 01.23
ss.SSS => 01.234
ss.SSSS => 01.2345
etc.

The current proposal is to *truncate* the result with no rounding.  This 
conforms to the general policy in DateFormat in which fields are not 
rounded, but truncated.  E.g.,  hh:mm does not display "1:31" if the time 
is 1:30:59.  However, the case of fractions of a second is perhaps 
different, since it is a non-integral field.  An alternate proposal is to 
implement simple HALF_UP rounding.

This will occur up to the limit of 1 nanosecond, that is, the maximum 
supported width is 9 characters: SSSSSSSSS.

Note: This behavior is *partially* implemented in ICU4C already, and not 
implemented at all in ICU4J.

Please reply with comments to this list.

[Alan S Liu/San Jose/IBM@IBMUS; [email protected];; IBM Globalization; 
5600 Cottle Road; San Jose, CA 95193;; (408) 256-3155]