src/share/classes/sun/text/resources/ja/FormatData_ja.java

*** 129,138 ****
--- 129,155 ----
                      "11", // abb november
                      "12", // abb december
                      ""    // abb month 13 if applicable
                  }
              },
+             { "MonthNarrows",
+                 new String[] {
+                     "1", // january
+                     "2", // february
+                     "3", // march
+                     "4", // april
+                     "5", // may
+                     "6", // june
+                     "7", // july
+                     "8", // august
+                     "9", // september
+                     "10", // october
+                     "11", // november
+                     "12", // december
+                     ""    // month 13 if applicable
+                 }
+             },
              { "DayNames",
                  new String[] {
                      "\u65e5\u66dc\u65e5", // Sunday
                      "\u6708\u66dc\u65e5", // Monday
                      "\u706b\u66dc\u65e5", // Tuesday