<ContentPage.Resources>
        <ResourceDictionary>

            <Style TargetType="telerik:TabViewHeader" x:Key="tabstripStyle">
                <Setter Property="Orientation" Value="Vertical"/>
                <Setter Property="SelectedIndex" Value="1"/>
            </Style>


        </ResourceDictionary>
    </ContentPage.Resources>
    <VerticalStackLayout>
        <telerik:RadDateTimePicker TabStripStyle="{StaticResource tabstripStyle}" x:Name="picker"/>
    </VerticalStackLayout>