CREATE TABLE table_66239 ("State  ( class ) " TEXT, "Vacator" TEXT, "Reason for change" TEXT, "Successor" TEXT, "Date of successor's formal installation" TEXT)

Which date of Date of successor's formal installation has a State (class) of michigan (2)?
SELECT "Date of successor's formal installation" FROM table_66239 WHERE "State (class)" = 'michigan (2)'
SELECT "Date of successor's formal installation" FROM "table_66239" WHERE "State (class)" = 'michigan (2)'