On one of the sites I maintain I have a main event module on one tab called "Group Runs". That is a calendar view showing a month at a time. Nearly all the events of that calendar are repeating every week often on multiple days. (for example every MOnday and Wendesday.)
On the main page of the site is a list view module that draws from that main event module and displays the current days events only in list form. In the 4.0.1 version this is broken. I used to be able to put on on Selected Days 0 days before the current date and 0 days after the current date. Now I have to put in 0 days before and 1 day after, and that displays two days of events.
The worked in 3.3.7 and before, broke in 3.3.8, worked in 4.0.0, but broke in 4.0.1.