Every four years.
"Endow with Thy spirit of wisdom those whom in Thy name we entrust the authority of government, that there may be justice and peace at home, and that through obedience to Thy law, we may show forth Thy praise among the nations of the earth. In time of prosperity fill our hearts with thankfulness, and in the day of trouble, suffer not our trust in Thee to fail; all of which we ask through Jesus Christ our Lord. Amen."-Thomas Jefferson