feat: WIP retire MonthView and YearView.

demo/Ursa.Demo/Pages/DatePickerDemo.axaml

@@ -8,6 +8,6 @@
     <StackPanel Margin="20" HorizontalAlignment="Left">
         <u:CalendarMonthView />
         <u:CalendarYearView />
-        <u:CalendarDisplayControl/>
+        <u:CalendarView/>
     </StackPanel>
 </UserControl>

src/Ursa.Themes.Semi/Controls/Calendar.axaml

@@ -5,7 +5,7 @@
     <Design.PreviewWith>
         <StackPanel Margin="20" Spacing="5">
             <u:CalendarMonthView />
-            <u:CalendarDisplayControl />
+            <u:CalendarView />
         </StackPanel>
     </Design.PreviewWith>
     <!--  Add Resources Here  -->
@@ -120,15 +120,15 @@
         </Style>
     </ControlTheme>
 
-    <ControlTheme x:Key="{x:Type u:CalendarDisplayControl}" TargetType="u:CalendarDisplayControl">
+    <ControlTheme x:Key="{x:Type u:CalendarView}" TargetType="u:CalendarView">
         <Setter Property="MinHeight" Value="300" />
         <Setter Property="Template">
-            <ControlTemplate TargetType="u:CalendarDisplayControl">
+            <ControlTemplate TargetType="u:CalendarView">
                 <Panel>
                     <Grid RowDefinitions="Auto, *">
                         <Grid Grid.Row="0" ColumnDefinitions="Auto, Auto,*, Auto, Auto">
                             <Button
-                                Name="{x:Static u:CalendarDisplayControl.PART_PreviousYearButton}"
+                                Name="{x:Static u:CalendarView.PART_PreviousYearButton}"
                                 Grid.Column="0"
                                 HorizontalContentAlignment="Left"
                                 Foreground="{TemplateBinding Foreground}"
@@ -141,7 +141,7 @@
                             </Button>
 
                             <Button
-                                Name="{x:Static u:CalendarDisplayControl.PART_PreviousButton}"
+                                Name="{x:Static u:CalendarView.PART_PreviousButton}"
                                 Grid.Column="1"
                                 HorizontalContentAlignment="Left"
                                 Foreground="{TemplateBinding Foreground}"
@@ -155,7 +155,7 @@
 
                             <Grid Grid.Column="2" ColumnDefinitions="*, *">
                                 <Button
-                                    Name="{x:Static u:CalendarDisplayControl.PART_YearButton}"
+                                    Name="{x:Static u:CalendarView.PART_YearButton}"
                                     Grid.Column="0"
                                     HorizontalContentAlignment="Center"
                                     Content="2024"
@@ -163,7 +163,7 @@
                                     IsVisible="{TemplateBinding IsMonthMode}"
                                     Theme="{DynamicResource BorderlessButton}" />
                                 <Button
-                                    Name="{x:Static u:CalendarDisplayControl.PART_MonthButton}"
+                                    Name="{x:Static u:CalendarView.PART_MonthButton}"
                                     Grid.Column="1"
                                     HorizontalContentAlignment="Center"
                                     Content="Apr"
@@ -171,7 +171,7 @@
                                     IsVisible="{TemplateBinding IsMonthMode}"
                                     Theme="{DynamicResource BorderlessButton}" />
                                 <Button
-                                    Name="{x:Static u:CalendarDisplayControl.PART_HeaderButton}"
+                                    Name="{x:Static u:CalendarView.PART_HeaderButton}"
                                     Grid.Column="0"
                                     Grid.ColumnSpan="2"
                                     IsVisible="{TemplateBinding IsMonthMode, Converter={x:Static BoolConverters.Not}}"
@@ -181,7 +181,7 @@
                             </Grid>
 
                             <Button
-                                Name="{x:Static u:CalendarDisplayControl.PART_NextButton}"
+                                Name="{x:Static u:CalendarView.PART_NextButton}"
                                 Grid.Column="3"
                                 HorizontalContentAlignment="Left"
                                 Foreground="{TemplateBinding Foreground}"
@@ -193,7 +193,7 @@
                                     Foreground="{DynamicResource CalendarItemIconForeground}" />
                             </Button>
                             <Button
-                                Name="{x:Static u:CalendarDisplayControl.PART_NextYearButton}"
+                                Name="{x:Static u:CalendarView.PART_NextYearButton}"
                                 Grid.Column="4"
                                 HorizontalContentAlignment="Left"
                                 Foreground="{TemplateBinding Foreground}"
@@ -206,12 +206,12 @@
                             </Button>
                         </Grid>
                         <u:CalendarMonthView
-                            Name="{x:Static u:CalendarDisplayControl.PART_MonthView}"
+                            Name="{x:Static u:CalendarView.PART_MonthView}"
                             Grid.Row="1"
                             VerticalAlignment="Top"
                             IsVisible="{TemplateBinding IsMonthMode}" />
                         <u:CalendarYearView
-                            Name="{x:Static u:CalendarDisplayControl.PART_YearView}"
+                            Name="{x:Static u:CalendarView.PART_YearView}"
                             Grid.Row="1"
                             Width="{Binding #PART_MonthView.Bounds.Width}"
                             Height="{Binding #PART_MonthView.Bounds.Height}"

src/Ursa/Controls/DateTimePicker/CalendarDisplayControl.cs

@@ -1,159 +0,0 @@
-using Avalonia;
-using Avalonia.Collections;
-using Avalonia.Controls;
-using Avalonia.Controls.Metadata;
-using Avalonia.Controls.Primitives;
-using Avalonia.Interactivity;
-using Irihi.Avalonia.Shared.Helpers;
-
-namespace Ursa.Controls;
-
-[TemplatePart(PART_NextYearButton, typeof(Button))]
-[TemplatePart(PART_PreviousYearButton, typeof(Button))]
-[TemplatePart(PART_NextButton, typeof(Button))]
-[TemplatePart(PART_PreviousButton, typeof(Button))]
-[TemplatePart(PART_YearButton, typeof(Button))]
-[TemplatePart(PART_MonthButton, typeof(Button))]
-[TemplatePart(PART_HeaderButton, typeof(Button))]
-[TemplatePart(PART_MonthView, typeof(CalendarMonthView))]
-[TemplatePart(PART_YearView, typeof(CalendarYearView))]
-public class CalendarDisplayControl: TemplatedControl
-{
-    public const string PART_NextYearButton = "PART_NextYearButton";
-    public const string PART_PreviousYearButton = "PART_PreviousYearButton";
-    public const string PART_NextButton = "PART_NextButton";
-    public const string PART_PreviousButton = "PART_PreviousButton";
-    public const string PART_YearButton = "PART_YearButton";
-    public const string PART_MonthButton = "PART_MonthButton";
-    public const string PART_MonthView = "PART_MonthView";
-    public const string PART_YearView = "PART_YearView";
-    public const string PART_HeaderButton = "PART_HeaderButton";
-
-    private CalendarMonthView? _monthView;
-    private CalendarYearView? _yearView;
-    // Year button only shows the year in month mode.
-    private Button? _yearButton;
-    // Month button only shows the month in month mode.
-    private Button? _monthButton;
-    // Header button shows year in year mode, and year range in higher mode. 
-    private Button? _headerButton;
-    
-    public event EventHandler<CalendarDayButtonEventArgs>? OnDateSelected;
-    public event EventHandler<CalendarDayButtonEventArgs>? OnDatePreviewed;
-
-    public static readonly StyledProperty<bool> IsTodayHighlightedProperty =
-        DatePickerBase.IsTodayHighlightedProperty.AddOwner<CalendarDisplayControl>();
-    public bool IsTodayHighlighted
-    {
-        get => GetValue(IsTodayHighlightedProperty);
-        set => SetValue(IsTodayHighlightedProperty, value);
-    }
-
-    public static readonly StyledProperty<DayOfWeek> FirstDayOfWeekProperty =
-        DatePickerBase.FirstDayOfWeekProperty.AddOwner<CalendarDisplayControl>();
-    
-    public DayOfWeek FirstDayOfWeek
-    {
-        get => GetValue(FirstDayOfWeekProperty);
-        set => SetValue(FirstDayOfWeekProperty, value);
-    }
-
-    private bool _isMonthMode = true;
-
-    public static readonly DirectProperty<CalendarDisplayControl, bool> IsMonthModeProperty = AvaloniaProperty.RegisterDirect<CalendarDisplayControl, bool>(
-        nameof(IsMonthMode), o => o.IsMonthMode, (o, v) => o.IsMonthMode = v);
-
-    public bool IsMonthMode
-    {
-        get => _isMonthMode;
-        set => SetAndRaise(IsMonthModeProperty, ref _isMonthMode, value);
-    }
-
-    protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
-    {
-        base.OnApplyTemplate(e);
-        if (_monthView is not null)
-        {
-            _monthView.OnDateSelected -= OnMonthViewDateSelected;
-            _monthView.OnDatePreviewed -= OnMonthViewDatePreviewed;
-        }
-
-        if (_yearView is not null)
-        {
-            _yearView.OnMonthSelected -= OnMonthSelected;
-        }
-        Button.ClickEvent.RemoveHandler(OnYearButtonClick, _yearButton);
-        Button.ClickEvent.RemoveHandler(OnMonthButtonClick, _monthButton);
-        Button.ClickEvent.RemoveHandler(OnHeaderButtonClick, _headerButton);
-        _monthView = e.NameScope.Find<CalendarMonthView>(PART_MonthView);
-        _yearView = e.NameScope.Find<CalendarYearView>(PART_YearView);
-        _yearButton = e.NameScope.Find<Button>(PART_YearButton);
-        _monthButton = e.NameScope.Find<Button>(PART_MonthButton);
-        _headerButton = e.NameScope.Find<Button>(PART_HeaderButton);
-        if(_monthView is not null)
-        {
-            _monthView.OnDateSelected += OnMonthViewDateSelected;
-            _monthView.OnDatePreviewed += OnMonthViewDatePreviewed;
-        }
-
-        if (_yearView is not null)
-        {
-            _yearView.OnMonthSelected += OnMonthSelected;
-        }
-        Button.ClickEvent.AddHandler(OnYearButtonClick, _yearButton);
-        Button.ClickEvent.AddHandler(OnMonthButtonClick, _monthButton);
-        Button.ClickEvent.AddHandler(OnHeaderButtonClick, _headerButton);
-    }
-
-    /// <summary>
-    /// Rule: 
-    /// </summary>
-    /// <param name="sender"></param>
-    /// <param name="e"></param>
-    private void OnHeaderButtonClick(object sender, RoutedEventArgs e)
-    {
-        if (_yearView?.Mode == CalendarYearViewMode.Month)
-        {
-            _headerButton?.SetValue(ContentControl.ContentProperty, _yearView.ContextDate.Year);
-            _yearView?.UpdateMode(CalendarYearViewMode.Year);
-        }
-        else if (_yearView?.Mode == CalendarYearViewMode.Year)
-        {
-            _headerButton?.SetCurrentValue(ContentControl.ContentProperty,
-                _yearView.ContextDate.Year + "-" + (_yearView.ContextDate.Year + 100));
-            _yearView?.UpdateMode(CalendarYearViewMode.YearRange);
-        }
-    }
-
-    private void OnMonthSelected(object sender, CalendarYearButtonEventArgs e)
-    {
-        SetCurrentValue(IsMonthModeProperty, true);
-    }
-
-    private void OnMonthButtonClick(object sender, RoutedEventArgs e)
-    {
-        SetCurrentValue(IsMonthModeProperty, false);
-        if (_yearView is null) return;
-        _headerButton?.SetValue(ContentControl.ContentProperty, _yearView.ContextDate.Year);
-        _yearView?.UpdateMode(CalendarYearViewMode.Month);
-    }
-
-    private void OnYearButtonClick(object sender, RoutedEventArgs e)
-    {
-        if (_yearView is null) return;
-        _headerButton?.SetValue(ContentControl.ContentProperty,
-            _yearView?.ContextDate.Year + "-" + (_yearView?.ContextDate.Year + 10));
-        _yearView?.UpdateMode(CalendarYearViewMode.Year);
-        SetCurrentValue(IsMonthModeProperty, false);
-    }
-
-    private void OnMonthViewDatePreviewed(object sender, CalendarDayButtonEventArgs e)
-    {
-        OnDatePreviewed?.Invoke(sender, e);
-    }
-
-    private void OnMonthViewDateSelected(object sender, CalendarDayButtonEventArgs e)
-    {
-        OnDateSelected?.Invoke(sender, e);
-    }
-}

src/Ursa/Controls/DateTimePicker/CalendarMonthView.cs

@@ -33,7 +33,7 @@ public class CalendarMonthView : TemplatedControl
             view.OnDayOfWeekChanged(args));
     }
 
-    internal CalendarDisplayControl? Owner { get; set; }
+    internal CalendarView? Owner { get; set; }
 
     /// <summary>
     ///     The DateTime used to generate the month view. This date will be within the month.

src/Ursa/Controls/DateTimePicker/CalendarView.cs

@@ -0,0 +1,275 @@
+using System.Globalization;
+using System.Reflection;
+using Avalonia;
+using Avalonia.Collections;
+using Avalonia.Controls;
+using Avalonia.Controls.Metadata;
+using Avalonia.Controls.Primitives;
+using Avalonia.Interactivity;
+using Avalonia.Layout;
+using Avalonia.Media.TextFormatting;
+using Irihi.Avalonia.Shared.Helpers;
+
+namespace Ursa.Controls;
+
+[TemplatePart(PART_NextYearButton, typeof(Button))]
+[TemplatePart(PART_PreviousYearButton, typeof(Button))]
+[TemplatePart(PART_NextButton, typeof(Button))]
+[TemplatePart(PART_PreviousButton, typeof(Button))]
+[TemplatePart(PART_YearButton, typeof(Button))]
+[TemplatePart(PART_MonthButton, typeof(Button))]
+[TemplatePart(PART_HeaderButton, typeof(Button))]
+[TemplatePart(PART_MonthView, typeof(CalendarMonthView))]
+[TemplatePart(PART_YearView, typeof(CalendarYearView))]
+[TemplatePart(PART_MonthGrid, typeof(Grid))]
+[TemplatePart(PART_YearGrid, typeof(Grid))]
+public class CalendarView: TemplatedControl
+{
+    public const string PART_NextYearButton = "PART_NextYearButton";
+    public const string PART_PreviousYearButton = "PART_PreviousYearButton";
+    public const string PART_NextButton = "PART_NextButton";
+    public const string PART_PreviousButton = "PART_PreviousButton";
+    public const string PART_YearButton = "PART_YearButton";
+    public const string PART_MonthButton = "PART_MonthButton";
+    public const string PART_MonthView = "PART_MonthView";
+    public const string PART_YearView = "PART_YearView";
+    public const string PART_HeaderButton = "PART_HeaderButton";
+    public const string PART_MonthGrid = "PART_MonthGrid";
+    public const string PART_YearGrid = "PART_YearGried";
+    
+    private const string ShortestDayName = "ShortestDayName";
+    
+    private readonly System.Globalization.Calendar _calendar = new GregorianCalendar();
+
+    internal CalendarViewMode Mode;
+
+    //private CalendarMonthView? _monthView;
+    //private CalendarYearView? _yearView;
+    private Grid? _monthGrid;
+    private Grid? _yearGrid;
+    // Year button only shows the year in month mode.
+    private Button? _yearButton;
+    // Month button only shows the month in month mode.
+    private Button? _monthButton;
+    // Header button shows year in year mode, and year range in higher mode. 
+    private Button? _headerButton;
+
+    public DateContext ContextDate { get; set; } = new DateContext();
+    
+    public event EventHandler<CalendarDayButtonEventArgs>? OnDateSelected;
+    public event EventHandler<CalendarDayButtonEventArgs>? OnDatePreviewed;
+
+    public static readonly StyledProperty<bool> IsTodayHighlightedProperty =
+        DatePickerBase.IsTodayHighlightedProperty.AddOwner<CalendarView>();
+    public bool IsTodayHighlighted
+    {
+        get => GetValue(IsTodayHighlightedProperty);
+        set => SetValue(IsTodayHighlightedProperty, value);
+    }
+
+    public static readonly StyledProperty<DayOfWeek> FirstDayOfWeekProperty =
+        DatePickerBase.FirstDayOfWeekProperty.AddOwner<CalendarView>();
+    
+    public DayOfWeek FirstDayOfWeek
+    {
+        get => GetValue(FirstDayOfWeekProperty);
+        set => SetValue(FirstDayOfWeekProperty, value);
+    }
+    
+    protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
+    {
+        base.OnApplyTemplate(e);
+
+        Button.ClickEvent.RemoveHandler(OnHeaderYearButtonClick, _yearButton);
+        Button.ClickEvent.RemoveHandler(OnHeaderMonthButtonClick, _monthButton);
+        Button.ClickEvent.RemoveHandler(OnHeaderButtonClick, _headerButton);
+  
+        _monthGrid = e.NameScope.Find<Grid>(PART_MonthGrid);
+        _yearGrid = e.NameScope.Find<Grid>(PART_YearGrid);
+        _yearButton = e.NameScope.Find<Button>(PART_YearButton);
+        _monthButton = e.NameScope.Find<Button>(PART_MonthButton);
+        _headerButton = e.NameScope.Find<Button>(PART_HeaderButton);
+
+        Button.ClickEvent.AddHandler(OnHeaderYearButtonClick, _yearButton);
+        Button.ClickEvent.AddHandler(OnHeaderMonthButtonClick, _monthButton);
+        Button.ClickEvent.AddHandler(OnHeaderButtonClick, _headerButton);
+        
+        GenerateGridElements();
+    }
+
+    /// <summary>
+    /// Rule: 
+    /// </summary>
+    /// <param name="sender"></param>
+    /// <param name="e"></param>
+    private void OnHeaderButtonClick(object sender, RoutedEventArgs e)
+    {
+        if (Mode == CalendarViewMode.Month)
+        {
+            throw new NotImplementedException();
+        }
+
+        if (Mode == CalendarViewMode.Year)
+        {
+            
+        }
+    }
+
+    /// <summary>
+    /// Generate Buttons and labels for MonthView.
+    /// Generate Buttons for YearView.  
+    /// </summary>
+    private void GenerateGridElements()
+    {
+        // Generate Day titles (Sun, Mon, Tue, Wed, Thu, Fri, Sat) based on FirstDayOfWeek and culture.
+        var count = 7 + 7 * 7;
+        var children = new List<Control>(count);
+        var dayOfWeek = (int)FirstDayOfWeek;
+        var info = DateTimeHelper.GetCurrentDateTimeFormatInfo();
+        for (var i = 0; i < 7; i++)
+        {
+            var d = (dayOfWeek + i) % DateTimeHelper.NumberOfDaysPerWeek;
+            var cell = new TextBlock { Text = info.ShortestDayNames[d], Tag = ShortestDayName };
+            cell.SetValue(HorizontalAlignmentProperty, HorizontalAlignment.Center);
+            cell.SetValue(Grid.RowProperty, 0);
+            cell.SetValue(Grid.ColumnProperty, i);
+            children.Add(cell);
+        }
+
+        // Generate day buttons.
+        for (var i = 2; i < DateTimeHelper.NumberOfWeeksPerMonth + 2; i++)
+        for (var j = 0; j < DateTimeHelper.NumberOfDaysPerWeek; j++)
+        {
+            var cell = new CalendarDayButton();
+            cell.SetValue(Grid.RowProperty, i);
+            cell.SetValue(Grid.ColumnProperty, j);
+            cell.AddHandler(CalendarDayButton.DateSelectedEvent, OnCellDateSelected);
+            cell.AddHandler(CalendarDayButton.DatePreviewedEvent, OnCellDatePreviewed);
+            children.Add(cell);
+        }
+        _monthGrid?.Children.AddRange(children);
+        
+        // Generate month/year buttons. 
+        for (var i = 0; i < 12; i++)
+        {
+            var button = new CalendarYearButton();
+            Grid.SetRow(button, i / 3);
+            Grid.SetColumn(button, i % 3);
+            button.AddHandler(CalendarYearButton.ItemSelectedEvent, OnYearItemSelected);
+            _yearGrid?.Children.Add(button);
+        }
+    }
+
+    private void RefreshButtons(DateTime date)
+    {
+        if (_monthGrid is null) return;
+        var children = _monthGrid.Children;
+        var info = DateTimeHelper.GetCurrentDateTimeFormatInfo();
+        var dayBefore = PreviousMonthDays(date);
+        var dateToSet = date.GetFirstDayOfMonth().AddDays(-dayBefore);
+        for (var i = 8; i < children.Count; i++)
+        {
+            var day = dateToSet;
+            var cell = children[i] as CalendarDayButton;
+            if (cell is null) continue;
+            cell.DataContext = day;
+            cell.IsToday = day == DateTime.Today;
+            cell.Content = day.Day.ToString(info);
+            dateToSet = dateToSet.AddDays(1);
+        }
+
+        FadeOutDayButtons();
+    }
+    
+    private void FadeOutDayButtons()
+    {
+        if (_monthGrid is null) return;
+        var children = _monthGrid.Children;
+        for (var i = 8; i < children.Count; i++)
+            if (children[i] is CalendarDayButton { DataContext: DateTime d } button && d.Month != ContextDate.Month)
+                button.IsNotCurrentMonth = true;
+    }
+    
+    private int PreviousMonthDays(DateTime date)
+    {
+        var firstDay = date.GetFirstDayOfMonth();
+        var dayOfWeek = _calendar.GetDayOfWeek(firstDay);
+        var firstDayOfWeek = FirstDayOfWeek;
+        var i = (dayOfWeek - firstDayOfWeek + DateTimeHelper.NumberOfDaysPerWeek) % DateTimeHelper.NumberOfDaysPerWeek;
+        return i == 0 ? DateTimeHelper.NumberOfDaysPerWeek : i;
+    }
+    
+    private void OnCellDatePreviewed(object sender, CalendarDayButtonEventArgs e)
+    {
+        OnDatePreviewed?.Invoke(sender, e);
+    }
+
+    private void OnCellDateSelected(object sender, CalendarDayButtonEventArgs e)
+    {
+        OnDateSelected?.Invoke(sender, e);
+    }
+
+    /// <summary>
+    /// Click on Month Header button. Calendar switch from month mode to year mode.
+    /// </summary>
+    /// <param name="sender"></param>
+    /// <param name="e"></param>
+    private void OnHeaderMonthButtonClick(object sender, RoutedEventArgs e)
+    {
+        _headerButton?.SetValue(ContentControl.ContentProperty, ContextDate.Year);
+        Mode = CalendarViewMode.Year;
+        IsVisibleProperty.SetValue(true, _yearGrid);
+        IsVisibleProperty.SetValue(false, _monthGrid);
+    }
+
+    /// <summary>
+    /// Click on Year Header button. Calendar switch from month mode to decade mode. 
+    /// </summary>
+    /// <param name="sender"></param>
+    /// <param name="e"></param>
+    private void OnHeaderYearButtonClick(object sender, RoutedEventArgs e)
+    {
+        if (_yearGrid is null) return;
+        int? decadeStart = ContextDate.Year / 10 * 10;
+        _headerButton?.SetValue(ContentControl.ContentProperty,
+            decadeStart + "-" + (decadeStart + 10));
+        Mode = CalendarViewMode.Decade;
+        IsVisibleProperty.SetValue(true, _yearGrid);
+        IsVisibleProperty.SetValue(false, _monthGrid);
+    }
+    
+    private void OnYearItemSelected(object sender, CalendarYearButtonEventArgs e)
+    {
+        if (_yearGrid is null) return;
+        var buttons = _yearGrid.Children.OfType<CalendarYearButton>().ToList();
+        if (e.Mode == CalendarViewMode.Year)
+        {
+            if (e.Month is null) return;
+            var day = MathHelpers.SafeClamp(e.Month.Value, 0,
+                DateTime.DaysInMonth(ContextDate.Year!.Value, e.Month.Value + 1));
+            ContextDate = new DateContext { Year = ContextDate.Year, Month = e.Month + 1, Day = day };
+            Mode = CalendarViewMode.Month;
+        }
+        else if (e.Mode == CalendarViewMode.Decade)
+        {
+            // Set CalendarYearView to Month mode
+            for (var i = 0; i < 12; i++)
+            {
+                buttons[i].SetValues(CalendarViewMode.Month, month: i);
+            }
+            ContextDate = new DateContext() { Year = e.Year!.Value, Month = ContextDate.Month, Day = null };
+            Mode = CalendarViewMode.Month;
+        }
+        else if (e.Mode == CalendarViewMode.Century)
+        {
+            // Set CalendarYearView to Year mode
+            for (var i = 0; i < 12; i++)
+            {
+                if (e.StartYear is null || e.EndYear is null) continue;
+                var year = e.StartYear.Value - 1 + i;
+                buttons[i].SetValues(CalendarViewMode.Year, year: year);
+            }
+            Mode = CalendarViewMode.Year;
+        }
+    }
+}

src/Ursa/Controls/DateTimePicker/CalendarViewMode.cs

@@ -0,0 +1,13 @@
+namespace Ursa.Controls;
+
+internal enum CalendarViewMode
+{
+    // Show days in current month.
+    Month,
+    // Show Months in current year.
+    Year,
+    // The button represents 10(12) years. 
+    Decade,
+    // The button represents 100(120) years.
+    Century,
+}

src/Ursa/Controls/DateTimePicker/CalendarYearButton.cs

@@ -8,15 +8,6 @@ using Irihi.Avalonia.Shared.Common;
 
 namespace Ursa.Controls;
 
-internal enum CalendarYearViewMode
-{
-    Month,
-    Year,
-
-    // The button represents 10 years. 
-    YearRange
-}
-
 [PseudoClasses(PC_Range, PseudoClassName.PC_Selected)]
 public class CalendarYearButton : ContentControl
 {
@@ -31,15 +22,15 @@ public class CalendarYearButton : ContentControl
         PressedMixin.Attach<CalendarYearButton>();
     }
 
-    internal int Year { get; private set; }
+    internal int? Year { get; private set; }
 
-    internal int Month { get; private set; }
+    internal int? Month { get; private set; }
 
-    internal int StartYear { get; private set; }
+    internal int? StartYear { get; private set; }
 
-    internal int EndYear { get; private set; }
+    internal int? EndYear { get; private set; }
 
-    internal CalendarYearViewMode Mode { get; private set; }
+    internal CalendarViewMode Mode { get; private set; }
 
     public event EventHandler<CalendarDayButtonEventArgs> ItemSelected
     {
@@ -47,7 +38,7 @@ public class CalendarYearButton : ContentControl
         remove => RemoveHandler(ItemSelectedEvent, value);
     }
 
-    internal void SetValues(CalendarYearViewMode mode, DateTime contextDate, int? month = null, int? year = null,
+    internal void SetValues(CalendarViewMode mode, int? month = null, int? year = null,
         int? startYear = null, int? endYear = null)
     {
         Debug.Assert(!(month is null && year is null && startYear is null && endYear is null));
@@ -58,9 +49,10 @@ public class CalendarYearButton : ContentControl
         EndYear = endYear ?? 0;
         Content = Mode switch
         {
-            CalendarYearViewMode.Month => DateTimeHelper.GetCurrentDateTimeFormatInfo().AbbreviatedMonthNames[Month],
+            CalendarViewMode.Month => DateTimeHelper.GetCurrentDateTimeFormatInfo().AbbreviatedMonthNames[Month.Value],
-            CalendarYearViewMode.Year => Year.ToString(),
+            CalendarViewMode.Year => Year.ToString(),
-            CalendarYearViewMode.YearRange => StartYear + "-" + EndYear,
+            CalendarViewMode.Decade => StartYear + "-" + EndYear,
+            CalendarViewMode.Century => StartYear + "-" + EndYear,
             _ => Content
         };
     }

src/Ursa/Controls/DateTimePicker/CalendarYearButtonEventArgs.cs

@@ -8,10 +8,10 @@ public class CalendarYearButtonEventArgs: RoutedEventArgs
     public int? Month { get; }
     public int? StartYear { get; }
     public int? EndYear { get; }
-    internal CalendarYearViewMode Mode { get; }
+    internal CalendarViewMode Mode { get; }
 
     /// <inheritdoc />
-    internal CalendarYearButtonEventArgs(CalendarYearViewMode mode, int? year, int? month, int? startYear, int? endYear )
+    internal CalendarYearButtonEventArgs(CalendarViewMode mode, int? year, int? month, int? startYear, int? endYear )
     {
         Year = year;
         Month = month;

src/Ursa/Controls/DateTimePicker/CalendarYearView.cs

@@ -20,7 +20,7 @@ public class CalendarYearView: TemplatedControl
 
     public event EventHandler<CalendarYearButtonEventArgs>? OnMonthSelected; 
 
-    internal CalendarYearViewMode Mode { get; set; } = CalendarYearViewMode.Month;
+    internal CalendarViewMode Mode { get; set; } = CalendarViewMode.Month;
     internal DateTime ContextDate { get; set; } = DateTime.Today;
 
     private Grid? _grid;
@@ -55,33 +55,33 @@ public class CalendarYearView: TemplatedControl
     {
         if (_grid is null) return;
         var buttons = _grid.Children.OfType<CalendarYearButton>().ToList();
-        if (e.Mode == CalendarYearViewMode.Month)
+        if (e.Mode == CalendarViewMode.Month)
         {
             if (e.Month is null) return;
             var day = MathHelpers.SafeClamp(e.Month.Value, 0, DateTime.DaysInMonth(ContextDate.Year, e.Month.Value+1));
             ContextDate = new DateTime(ContextDate.Year, e.Month.Value+1, day+1);
             OnMonthSelected?.Invoke(this, e);
         }
-        else if (e.Mode == CalendarYearViewMode.Year)
+        else if (e.Mode == CalendarViewMode.Year)
         {
             // Set CalendarYearView to Month mode
             for (var i = 0; i < 12; i++)
             {
-                buttons[i].SetValues(CalendarYearViewMode.Month, ContextDate, month: i);
+                buttons[i].SetValues(CalendarViewMode.Month, month: i);
             }
             ContextDate = new DateTime(e.Year!.Value, ContextDate.Month, 1);
-            Mode = CalendarYearViewMode.Month;
+            Mode = CalendarViewMode.Month;
         }
-        else if (e.Mode == CalendarYearViewMode.YearRange)
+        else if (e.Mode == CalendarViewMode.Decade)
         {
             // Set CalendarYearView to Year mode
             for (var i = 0; i < 12; i++)
             {
                 if (e.StartYear is null || e.EndYear is null) continue;
                 var year = e.StartYear.Value - 1 + i;
-                buttons[i].SetValues(CalendarYearViewMode.Year, ContextDate, year: year);
+                buttons[i].SetValues(CalendarViewMode.Year, year: year);
             }
-            Mode = CalendarYearViewMode.Year;
+            Mode = CalendarViewMode.Year;
         }
     }
 
@@ -96,22 +96,22 @@ public class CalendarYearView: TemplatedControl
             if (child is null) continue;
             switch (mode)
             {
-                case CalendarYearViewMode.Month:
+                case CalendarViewMode.Month:
-                    child.SetValues(CalendarYearViewMode.Month, contextDate, month: i);
+                    child.SetValues(CalendarViewMode.Month, month: i);
                     break;
-                case CalendarYearViewMode.Year:
+                case CalendarViewMode.Year:
-                    child.SetValues(CalendarYearViewMode.Year, contextDate, year: ContextDate.Year / 10 * 10 + i - 1);
+                    child.SetValues(CalendarViewMode.Year, year: ContextDate.Year / 10 * 10 + i - 1);
                     break;
-                case CalendarYearViewMode.YearRange:
+                case CalendarViewMode.Decade:
                     var startYear = (ContextDate.Year / 10 + i - 1) * 10;
                     var endYear = (ContextDate.Year / 10 + i - 1) * 10 + 10;
-                    child.SetValues(CalendarYearViewMode.YearRange, contextDate, startYear: startYear, endYear: endYear);
+                    child.SetValues(CalendarViewMode.Decade, startYear: startYear, endYear: endYear);
                     break;
             }
         }
     }
 
-    internal void UpdateMode(CalendarYearViewMode mode)
+    internal void UpdateMode(CalendarViewMode mode)
     {
         Mode = mode;
         RefreshButtons();

src/Ursa/Controls/DateTimePicker/DateContext.cs

@@ -0,0 +1,8 @@
+namespace Ursa.Controls;
+
+public class DateContext(int? year = null, int? month = null, int? day = null)
+{
+    public int? Year = year;
+    public int? Month = month;
+    public int? Day = day;
+}