It is the duty of the county legislative bodies, on the first Monday in July, or as soon thereafter as practicable, to fix the tax rates on all properties within their respective jurisdictions for all county purposes, except that in any county having a population in excess of seven hundred thousand (700,000), according to the 1980 federal census or any subsequent federal census, establishing tax due dates other than the first Monday in October each year, in accordance with § 67-1-701(a), shall have the authority to fix tax rates for all county purposes at dates prior to the first Monday in July.