After the result of an election is declared, or when an appointment is made, the city clerk under his or her hand and official seal, shallissue a certificate therefor and serve the same personally or by depositing such certificate with the postage prepaid, in the United States post office in Petaluma, addressed to the person elected or appointed, and such person must, within sixty days after receiving such certificate, file his official bond, if a bond is required of him by this Charter or the ordinances of the city, and take and subscribe to the oath of office and any other oath required of him by this Charter or any statute of the State of California which oath must be filed with the city clerk. All elective officers shall take office at the first regular meeting of the city council in January after the result of each election shall have been officially declared, and shall hold office for such term as in this Charter provided and until the election and qualification of their successors.