Cell overflow popover widget does not position itself correctly when near the bottom of the screen
If you have GNOME calendar near the bottom edge of the screen and a cell in the month's last week overflows with events, clicking the "+3 more" button will show a truncated popover widget because it will align its top with the top of the cell, instead of aligning the bottom of the popover with the bottom of GNOME Calendar's window/screen:
As a floating window, non-expanded:
Expanded:
Truncated result if the window is maximized/at the bottom of the screen: