Are you using a capital D for the date? That would seem to get interpreted as the Julian date (i.e. the day of the year, from 1 to 366).
From the Windchill Customization Guide, Windchill 10.1, November 2014, M050, Document Version 10.1.06 (pages 695-698; i.e. a chart split across four pages):
Property Name: Date Display Format
Applicable attribute data types: Date
Description: A date format string (i.e. yyyy-mm-dd) to use when displaying the value of this attribute in View mode. This does not affect the format used to set the value in input mode. Please refer to the Java class java.text.Simple-DateFormat for the full set of valid characters. If not set, one of the following formats will be used from the rbInfo file componentRB:
-- STANDARD_DATE_DISPLAY_FORMAT - if the value of the property "Date Input Field Type" is set to "Date Only", this format will be used.
-- STANDARD_DATE_TIME_ZONE_DISPLAY_FORMAT - if the value of the property "Date Input Field Type" is not set or is set to "Date and Time", this format will be used.
Preference (The configuration applies to all attributes, in all clients): Not available at this level.
Type and attribute Management utility attribute Definition 1: If not specified, the default will be used.
Type and attribute Management utility attribute Panel Layout Definition 2 OR ComponentConfig 3: If not specified, the value of this property from the Attribute Definition will be used, if that has Presenting Information in the UI 695 been specified. Otherwise the default will be used. OR setDateDisplayFormat()
So searching for the Java class gives:SimpleDateFormat (Java Platform SE 7 ) gives:
Letter; Date or Time Component; Presentation; Examples
D; Day in year; Number; 189
d; Day in month; Number; 10
Another possibility: try it with the four-digit year format "yyyy" Date-time fields are sometimes context-sensitive, where including / excluding certain codes will change the behavior of other codes (short example, in Excel, format "hh:mm" will use a 24-hour clock, but "hh:mm am/pm" will use a 12-hour clock).
