CREATE TABLE table_24501 ("District" TEXT, "Vacator" TEXT, "Reason for change" TEXT, "Successor" TEXT, "Date successor seated" TEXT)

On what date was James P. Buchanan (d)'s successor seated?
SELECT "Date successor seated" FROM table_24501 WHERE "Vacator" = 'James P. Buchanan (D)'
SELECT "Date successor seated" FROM "table_24501" WHERE "Vacator" = 'James P. Buchanan (D)'