Except when otherwise expressly provided, the regular term of office for all county officers, when elected for a full term, shall commence on the first Monday in January next succeeding their election, except the office of county auditor, the term of which shall begin on the first Monday of March next succeeding his election. If the office to which any officer was elected be vacant at the time of his election, or becomes vacant after such election, even if he was not elected to fill a vacancy, he shall forthwith qualify and enter upon the duties of his office.
SDCL 7-7-1