Better late than never, I guess....
Illinois Administrative Code
Section 110.100 Finance Charges – Rebates and Delinquency Charges
b) A standard payment schedule is one under which a loan is repayable in substantially equal and consecutive monthly installments of principal and charges combined, and the first installment is due one month from the date of the note, except as provided in subjsections (b)(1) and (2).
1) The loan contract shall be drawn to reflect a standard payment schedule with payments to be made on a calendar month basis, except that the first installment period may exceed one month by as much as 15 days. If a charge is made for extra days in the first installment period it may be added to the first installment payment. The interest for such period may be increased by 1/30 of the agreed monthly rate for each extra day. A charge for extra days in the first installment period does not change the amount of rebate required for prepayment in full on or after the first installment date.