You can hide the dates from the previous and last months through a CalendarDelegate and UpdateVisualsForCell method, however, keep in mind that this will not affect the calculations that the calendar does to position its cells and it will still display 6 rows.
Here is a quick snippet:
CustomCalendarDelegate : CalendarDelegate
UpdateVisualsForCell(TKCalendar calendar, TKCalendarCell cell)
var dayCell = cell
dayCell.Hidden = (dayCell.State & TKCalendarDayState.CurrentMonth) == 0;
For additional information, please check Calendar Customizations
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