Casino executives say it's a result of higher state gambling taxes that lawmakers approved this spring.
State gambling regulators say gamblers might choose to go to neighboring states where casinos are open 24 hours.
The Illinois Gaming Board today approved requests from Alton Belle Casino, Empress Casino in Joliet, Harrah's Casino in Joliet and Hollywood Casino in Aurora to change their operating hours to 10 a-m to 4 a-m.
Interim Board Administrator Jeannette Tamayo says she doesn't know how the reduced hours will affect state revenues. She says the hours that are being cut typically bring in less money.