When Blake arrives home, his mother is listening to a radio show that states it is a Saturday afternoon program, but the next morning (which should be Sunday) Katie gets on a bus to go to school.
The calendar in the newspaper office shows a month beginning on a Wednesday, but the calendar in the police station shows a month beginning on a Monday. The second calendar is seen a day or two after the first, so one might argue it's a new month, but it is impossible for any month to begin on a Monday if the previous month began on a Wednesday.