The term of office of all officers chosen at a general election for a full term shall commence on the first day of January following the election which is not a Sunday or legal holiday, except when otherwise provided by the Constitution or by statute; that of an officer chosen to fill a vacancy shall commence as soon as the officer has qualified therefor.
Iowa Code § 39.8
Governor and lieutenant governor, Iowa Constitution, Art. IV, §15
Judges of supreme and district courts, Iowa Constitution, Art. V, §17