55 ILCS 5/3-10008
Except as otherwise provided in this Section, the county treasurer shall keep his office open and attend to the duties thereof from eight o'clock in the forenoon to five o'clock in the afternoon on each working day excepting such days as under law are legal holidays, and may close his office at 12 o'clock on Saturday of each week; Provided, that the county treasurer shall not be compelled to open his office before the hour of nine o'clock a. m. and, by permission of the county board, the treasurer may close his office all day Saturday: Provided, further, that, except with respect to the required office hours applicable to tax sales, the hours of opening and closing of the office of the county treasurer may be changed and otherwise fixed and determined by the county board of any county. Any such action taken by the county board shall be by an appropriate resolution passed at a regular meeting. Notwithstanding the provisions of this Section or any other provision of law, the county treasurer must keep his or her office open from 8:00 a.m. until 4:00 p.m. on the business day before the commencement of a tax sale held in the county pursuant to Division 3.5 of Article 21 of the Property Tax Code and during the same hours each day the tax sale is pending. A home rule unit may not regulate the hours employed by the county treasurer in a manner that is inconsistent with this Section. This Section is a limitation under subsection (i) of Section 6 of Article VII of the Illinois Constitution on the concurrent exercise by home rule units of powers and functions exercised by the State.
55 ILCS 5/3-10008