Added date format yyyy/mm/dd

cell.go

@@ -313,6 +313,8 @@ func (c *Cell) FormattedValue() string {
 		return c.formatToTime("02/01/06\\ 15:04")
 	case "dd/mm/yyyy hh:mm:ss":
 		return c.formatToTime("02/01/2006 15:04:05")
+	case "yyyy/mm/dd":
+		return c.formatToTime("2006/01/02")
 	case "yy-mm-dd":
 		return c.formatToTime("06-01-02")
 	case "d-mmm-yyyy":

cell_test.go

@@ -221,6 +221,9 @@ func (l *CellSuite) TestFormattedValue(c *C) {
 	cell.numFmt = "dd/mm/yy\\ hh:mm"
 	c.Assert(cell.FormattedValue(), Equals, "22/11/03\\ 18:00")
 
+	cell.numFmt = "yyyy/mm/dd"
+	c.Assert(cell.FormattedValue(), Equals, "2003/11/22")
+
 	cell.numFmt = "yy-mm-dd"
 	c.Assert(cell.FormattedValue(), Equals, "03-11-22")