CREATE TABLE table_73400 ("District" TEXT, "Vacator" TEXT, "Reason for change" TEXT, "Successor" TEXT, "Date successor seated" TEXT)

What is the date successor seated where Massachusetts 2nd is the district?
SELECT "Date successor seated" FROM table_73400 WHERE "District" = 'Massachusetts 2nd'
SELECT "Date successor seated" FROM "table_73400" WHERE "District" = 'Massachusetts 2nd'