All persons interested in the original assessment, or in the lands affected thereby or in the bonds secured thereby, may, at the time of the hearing or at the time to which the hearing may be continued, appear and protest against the amended assessment. At the hearing the legislative body shall hear and determine all objections to the division of the assessments and shall confirm or modify the same. All determinations and decisions of the legislative body shall be conclusive upon all persons entitled to object under the provisions of this section. Final action of the legislative body upon the report and amended assessment shall be taken on or before the fifteenth day of July of any year.