Avalonia DateTimePicker

App.axaml

<Application xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="using:AvaloniaTest"
             xmlns:v="using:AvaloniaTest.Views"
             x:Class="AvaloniaTest.App">
  <Application.DataTemplates>
    <local:ViewLocator/>
  </Application.DataTemplates>

  <Application.Styles>
    <FluentTheme Mode="Light"/>
    <Style Selector="v|FBCDateTimePickerPresenter" >
      <Setter Property="Template">
        <ControlTemplate>
          <Grid ColumnDefinitions="Auto, Auto" RowDefinitions="Auto,40" Background="White">
            <Grid.Styles>
              <Style Selector="Grid" >
                <Setter Property="VerticalAlignment"  Value="Center"/>
              </Style>
              <Style Selector="Calendar">
                <Setter Property="HorizontalAlignment"  Value="Center"/>
                <Setter Property="Margin" Value="10"/>
              </Style>
              <Style Selector="NumericUpDown">
                <Setter Property="VerticalAlignment"  Value="Top"/>
                <Setter Property="BorderBrush" Value="Orange"/>
                <Setter Property="Margin" Value="0,10,10,0"/>
              </Style>
              <Style Selector="TextBlock" >
                <Setter Property="HorizontalAlignment" Value="Center"/>
                <Setter Property="VerticalAlignment"  Value="Bottom"/>
                <Setter Property="Margin" Value="0,10,0,0"/>
              </Style>
              <Style Selector="Button" >
                <Setter Property="HorizontalAlignment" Value="Center"/>
                <Setter Property="VerticalAlignment"  Value="Center"/>
                <Setter Property="BorderBrush" Value="Orange"/>
              </Style>
            </Grid.Styles>
            <Calendar SelectedDate="{TemplateBinding DateOnly}"/>
            <Grid Grid.Column="1" RowDefinitions="1*,1*,1*,1*,1*,1*">
              <TextBlock Grid.Row="0" Text="Saat" />
              <NumericUpDown Name="Hour" Grid.Row="1"  Minimum="0" Maximum="23" Value="{TemplateBinding Hour}"/>
              <TextBlock Grid.Row="2"  Text="Dakika" />
              <NumericUpDown Name="Minute"  Grid.Row="3"  Minimum="0" Maximum="59" Value="{TemplateBinding Minute}"/>
              <TextBlock Grid.Row="4"  Text="Saniye" />
              <NumericUpDown Name="Second"  Grid.Row="5"  Minimum="0" Maximum="59" Value="{TemplateBinding Second}"/>
            </Grid>
            <Grid Grid.Row="2" Grid.ColumnSpan="2" ColumnDefinitions="1*, 1*">
              <Button Grid.Column="0" Content="Tamam" Name="BtnOK"/>
              <Button Grid.Column="1" Content="Vazgeç" Name="BtnCancel"/>
            </Grid>
          </Grid>
        </ControlTemplate>
      </Setter>
    </Style>
  </Application.Styles>

</Application>

FBCDateTimePickerPresenter.cs

using Avalonia;
using Avalonia.Controls.Primitives;
using System;
using Avalonia.Interactivity;
using Avalonia.Controls;

namespace AvaloniaTest.Views
{
    /// <summary>
    /// FBC: My references
    /// https://github.com/AvaloniaUI/Avalonia/blob/master/src/Avalonia.Controls/DateTimePickers/DatePicker.cs
    /// https://github.com/AvaloniaUI/Avalonia/blob/master/src/Avalonia.Themes.Default/DatePicker.xaml
    /// https://github.com/AvaloniaUI/Avalonia/blob/master/src/Avalonia.Controls/DateTimePickers/DatePickerPresenter.cs
    /// </summary>
    public class FBCDateTimePickerPresenter : PickerPresenterBase
    {
        public FBCDateTimePickerPresenter(): base()
        {
            Value = DateTime.Now;
        }

        public static readonly DirectProperty<FBCDateTimePickerPresenter, DateTime> DateOnlyProperty =
            AvaloniaProperty.RegisterDirect<FBCDateTimePickerPresenter, DateTime>(nameof(DateOnly),
                x => x.DateOnly, (x, v) => x.DateOnly = v);

        public static readonly DirectProperty<FBCDateTimePickerPresenter, int> HourProperty =
            AvaloniaProperty.RegisterDirect<FBCDateTimePickerPresenter, int>(nameof(Hour),
                x => x.Hour, (x, v) => x.Hour = v);

        public static readonly DirectProperty<FBCDateTimePickerPresenter, int> MinuteProperty =
            AvaloniaProperty.RegisterDirect<FBCDateTimePickerPresenter, int>(nameof(Minute),
                x => x.Minute, (x, v) => x.Minute = v);

        public static readonly DirectProperty<FBCDateTimePickerPresenter, int> SecondProperty =
            AvaloniaProperty.RegisterDirect<FBCDateTimePickerPresenter, int>(nameof(Second),
                x => x.Second, (x, v) => x.Second = v);


        private DateTime dateOnly;
        private  int hour;
        private  int minute;
        private  int second;

        public DateTime DateOnly
        {
            get { return dateOnly; }
            set
            {
                SetAndRaise(DateOnlyProperty, ref dateOnly, value);
            }
        }

        public int Hour
        {
            get { return hour; }
            set
            {
                SetAndRaise(HourProperty, ref hour, value);
            }
        }
        public int Minute
        {
            get { return minute; }
            set
            {
                minute = value;
                SetAndRaise(MinuteProperty, ref minute, value);
            }
        }
        public int Second
        {
            get { return second; }
            set
            {
                second = value;
                SetAndRaise(SecondProperty, ref second, value);
            }
        }
        NumericUpDown nuHour;
        NumericUpDown nuMinute;
        NumericUpDown nuSecond;
        Button BtnOK;
        Button BtnCancel;
        protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
        {
            base.OnApplyTemplate(e);
            nuHour = e.NameScope.Get<NumericUpDown>("Hour");
            nuMinute = e.NameScope.Get<NumericUpDown>("Minute");
            nuSecond = e.NameScope.Get<NumericUpDown>("Second");
            BtnOK = e.NameScope.Get<Button>("BtnOK");
            BtnCancel = e.NameScope.Get<Button>("BtnCancel");

            if (BtnOK != null)
            {
                BtnOK.Click += OnAcceptButtonClicked;
            }
            if (BtnCancel != null)
            {
                BtnCancel.Click += OnDismissButtonClicked;
            }

        }

        private void OnDismissButtonClicked(object? sender, RoutedEventArgs e)
        {
            OnDismiss();
        }

        private void OnAcceptButtonClicked(object? sender, RoutedEventArgs e)
        {
            //Date = _syncDate;
            OnConfirmed();
        }

        public DateTime Value
        {
            get { return new DateTime(DateOnly.Year, DateOnly.Month, DateOnly.Day, Hour, Minute, Second); }
            set
            {
                DateOnly = value.Date;
                Hour = value.Hour;
                Minute = value.Minute;
                Second = value.Second;
                //OnPropertyChanged();
            }
        }

    }
}

MainWindow.axaml

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="using:AvaloniaTest.ViewModels"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
        x:Class="AvaloniaTest.Views.MainWindow"
        Icon="/Assets/avalonia-logo.ico"
        xmlns:v="using:AvaloniaTest.Views"
        Title="AvaloniaTest">
  <Design.DataContext>
    <vm:MainWindowViewModel/>
  </Design.DataContext>
  <StackPanel Orientation="Vertical" VerticalAlignment="Center">
    <Button Content="Popeye"  Name="sabri"/>
    <Popup Name="Popup"
           WindowManagerAddShadowHint="False"
           StaysOpen="False"
           PlacementMode="Bottom"
           PlacementTarget="{Binding ElementName=sabri}">
      <v:FBCDateTimePickerPresenter Name="PopPresenter"/>
    </Popup>
  </StackPanel>
</Window>

MainWindow.axaml.cs

using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.Primitives;
using Avalonia.Markup.Xaml;

namespace AvaloniaTest.Views
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
#if DEBUG
            this.AttachDevTools();
#endif
        }
        Button sabri;
        Popup pop;
        FBCDateTimePickerPresenter popPresenter;
        private void InitializeComponent()
        {
            AvaloniaXamlLoader.Load(this);
            sabri = this.FindControl<Button>("sabri");
            pop = this.FindControl<Popup>("Popup");
            popPresenter = this.FindControl<FBCDateTimePickerPresenter>("PopPresenter");
            popPresenter.Confirmed += PopPresenter_Confirmed;
            popPresenter.Dismissed += PopPresenter_Dismissed;
            sabri.Tapped += Sabri_Tapped;

        }

        private void PopPresenter_Dismissed(object? sender, System.EventArgs e)
        {
            pop.Close();
            sabri.Content = "Cancelled";

        }

        private void PopPresenter_Confirmed(object? sender, System.EventArgs e)
        {
            pop.Close();
            sabri.Content = "New value is:" + popPresenter.Value;
        }

        private void Sabri_Tapped(object? sender, Avalonia.Interactivity.RoutedEventArgs e)
        {

            pop.IsOpen = true;

        }
    }
}