(elmo-msgdb-overview-entity-get-cc entity))))
      ((or (string= key "since")
          (string= key "before"))
-      (let ((field-date (timezone-make-date-sortable
+      (let ((field-date (elmo-date-make-sortable-string
                         (timezone-fix-time
                          (elmo-msgdb-overview-entity-get-date entity)
                          (current-time-zone) nil)))
 
                      (string-to-int (elmo-filter-value condition)))))
      ((string= (elmo-filter-key condition) "since")
       (let* ((date (elmo-date-get-datevec (elmo-filter-value condition)))
-            (field-date (timezone-make-date-sortable
+            (field-date (elmo-date-make-sortable-string
                          (timezone-fix-time
                           (std11-field-body "date")
                           (current-time-zone) nil)))