Fix clear year and month field when converting to biblatex

src/main/java/org/jabref/logic/cleanup/ConvertToBiblatexCleanup.java

@@ -39,6 +39,12 @@ public List<FieldChange> cleanup(BibEntry entry) {
                 entry.clearField(StandardField.YEAR).ifPresent(changes::add);
                 entry.clearField(StandardField.MONTH).ifPresent(changes::add);
             });
+        } else {
+            // If field date is filled it should be removed the year and month fields
+            entry.getFieldOrAlias(StandardField.DATE).ifPresent(newDate -> {
+                entry.clearField(StandardField.YEAR).ifPresent(changes::add);
+                entry.clearField(StandardField.MONTH).ifPresent(changes::add);
+            });
         }
         return changes;
     }