I want something which can hold all of these and be able to pass it to another form.
This "something" is called QWidget. You can create your CalendarForm as custom QWidget with all those buttons, layouts etc.
If this class ie CalenderForm can return a layout or somethin which i can use it in another form.
You can create one instance of this class and add it to a layout, remove from layout, add to another layout etc. This class don't need to return anything, the class is a "container" itself.