When I create a calendar, without changing its style, I see that the corner of the calendar is not covered fully by its corner.
This is more obvious when the focus is on it and the border is blue. I think there is a problem somewhere.
What MCU/Processor/Board and compiler are you using?
stm32f429, CubeIDE, GCC
What do you expect?
Border cover the calendar fully.
Code to reproduce
What LVGL version are you using?