f:action>
                                    <xf:action if="$c != ''">
                                        <xxf:variable select="if (year castable as xs:integer) then format-number(xs:integer(year), '0000') else '____'" name="y" as="xs:string"></xxf:variable>
                                        <xxf:variable select="if (month castable as xs:integer) then format-number(xs:integer(month), '00') else '__'" name="m" as="xs:string"></xxf:variable>
                                        <xxf:variable se