I'm using Excel 2003 with a standard Date cell format of "*3/14/2001". This is format index 14 (according to ExtendedFormatRecord). When I call HSSFDataFormat.getBuiltinFormat(14), I get mm/dd/yy. I was expecting mm/dd/yyyy. In another related issue, I use date format "3/14/2001". This format should be a built in format, but it's index returns as 165. When I get the FormatRecord, the format string shows as "m/d/yyyy;@". I was expecting m/d/yyyy.
Any chance you could upload a spreadsheet where this is happening, so we have something to test against?
Closing as no further information has been provided. Please re-open if you do have the spreadsheet In general though, newer versions of excel do seem to like using more complex "user defined" formats, instead of the older built in ones