While testing our app around timezones, we found a case where the cell selection would not render if timezone was set to Portugal, Azores (GMT+00:00). Selector reappears after switching to another month though. For some weird reason we were not able to replicate this issue for a similar timezone like Casablanca, Morocco (GMT+00:00).

When the Start and EndDate properties are changed one after another and each of them calls PropertyChanged the appointment does not render accurately. If for example there is an appointment from 3 PM to 4 PM (duration 1 hour) and the Appointment is changed to one hour earlier (from 2 PM to 3 PM) on the screen the Appointment is displayed from 2 PM to 4 PM (duration 2 hours).

Currently the first label marking the DayStartTime is not visualized in the timeline of the DayView (and MultiDayView) on Android. This leads to inconsistency with iOS, where the first label is displayed.

when showing 3 months (last month, present month and the next month) on calendar component, the next month tab is displayed twice. see the attached video

I've attached a handler to the ViewChanged event of the Calendar component.

The event fires on Android but not on UWP. I've tried changing the view type using the calendar controls and also programatically but the event is not being fired.

If you set SelectedDate when the Calendar control is created, does not take any effect in the UI on iOS. 

As a workaround, set SelectedDate at a later stage.

The visual representation of an appointment is wrong when DayViewSettings.StartTime is set so that the appointment is initially visible

when the RadCalendar is hosted inside a ScrollView, users cannot navigate to other month using the swipe gesture

When we have overlapping appointments in DayView with different Start and End times, TimeSlotTapped is not triggered for empty slots in between appointments.

When in MonthView, you're navigating to WeekView on CellTap event, and DisplayDate and SelectedDate are bound to the same value, DisplayDate is not updated on iOS (works properly on Android)

The more appointments you add to the AppointmentsSource, the poorer the performance of the Calendar is. 

This can be observed when switching months in month view. In case you have a huge amount of appointments, switching the months takes time. The issue is specifically obvious when a single month contains lots of appointments(600 for example). However, it is present when you are switching months that do not have any appointments at all as well.