Based on guidance we received from the Illinois Department of Financial and Professional Regulation (IDFPR), we do not see a problem with remaining closed two days per week, on Saturdays plus another day (such as Thursdays). The Promissory Note and Bank Holiday Act states that a bank may “select any one day of the week to remain closed on a regular basis,” provided that the bank’s board adopts a resolution and files and publishes the resolution as required. 205 ILCS 630/17(b). There is some ambiguity in the law, since Saturday is only a half holiday under Paragraph 17(a) — it is not clear whether a bank (or branch) may remain closed for Saturday and another day of the week. However, when we requested clarification from the IDFPR’s legal department, we were told that a bank may remain closed for Saturday :

The Act allows a bank to be closed for the half holiday on Saturday and one other day of the week.  So to answer the question – yes. The bank may choose any day (such as Thursday) to be closed in addition to the half holiday on Saturdays.