source: npl/overig/libical/libical-nth-recur-overflow.diff

src/libical/icalrecur.c

@@ -2140 +2140 @@
                 } else if (pos > 0) {
                     /* Add the nth instance of the weekday within the month. */
                     month_day = first_matching_day + (pos - 1) * 7;
+                    
+                    /* Track back overflowing days */
+                    while(month_day > days_in_month)
+                        month_day -=7;
 
                     if (month_day <= days_in_month)
                         impl->days[days_index++] = (short)(doy_offset + month_day);