ALTER TABLE "#__menu" ADD COLUMN "publish_up" timestamp without time zone;
ALTER TABLE "#__menu" ADD COLUMN "publish_down" timestamp without time zone;

ALTER TABLE "#__menu" ALTER COLUMN "checked_out_time" DROP NOT NULL;
ALTER TABLE "#__menu" ALTER COLUMN "checked_out_time" DROP DEFAULT;

UPDATE "#__menu" SET "checked_out_time" = NULL WHERE "checked_out_time" = '1970-01-01 00:00:00';