Highlighted WPF Calendar Control

HighlightCalendar.xaml

<Window x:Class="HighlightCalendar.HighlightCalendarWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:HighlightCalendar"
        mc:Ignorable="d"
        Title="HighlightCalendarWindow" Height="350" Width="525" Loaded="Window_Loaded">
    <Grid>
        <Viewbox VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
            <Calendar x:Name="calendar">
                <Calendar.CalendarDayButtonStyle>
                    <Style TargetType="CalendarDayButton" BasedOn="{StaticResource {x:Type CalendarDayButton}}">
                        <EventSetter Event="Loaded" Handler="calendarButton_Loaded" />
                    </Style>
                </Calendar.CalendarDayButtonStyle>
            </Calendar>
        </Viewbox>
    </Grid>
</Window>

HighlightCalendar.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace HighlightCalendar
{
	public partial class HighlightCalendarWindow : Window
	{
		private List<DateTime> significantDates;

		public HighlightCalendarWindow()
		{
			InitializeComponent();
		}

		private void Window_Loaded(object sender, RoutedEventArgs e)
		{
			significantDates = new List<DateTime>
			{
				DateTime.Parse("2016/11/15"),
				DateTime.Parse("2016/11/26"),
				DateTime.Parse("2016/11/30")
			};
		}

		private void calendarButton_Loaded(object sender, EventArgs e)
		{
			CalendarDayButton button = (CalendarDayButton)sender;
			DateTime date = (DateTime)button.DataContext;
			HighlightDay(button, date);
			button.DataContextChanged += new DependencyPropertyChangedEventHandler(calendarButton_DataContextChanged);
		}

		private void HighlightDay(CalendarDayButton button, DateTime date)
		{
			if (significantDates.Contains(date))
				button.Background = Brushes.LightBlue;
			else
				button.Background = Brushes.White;
		}

		private void calendarButton_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
		{
			CalendarDayButton button = (CalendarDayButton)sender;
			DateTime date = (DateTime)button.DataContext;
			HighlightDay(button, date);
		}
	}
}