How to show real-time clock using MVVM pattern?

public class MainPageViewModel : INotifyPropertyChanged
    {
        private string _currentTime;
        private string _currentDate;
        public string currentTime
        {
            get
            {
                return _currentTime;
            }
            set
            {
                _currentTime = value;
                OnPropertyChanged("currentTime");
            }
        }

        public MainPageViewModel()
        {
            #region RealTime Clock
            System.Windows.Threading.DispatcherTimer Timer = new System.Windows.Threading.DispatcherTimer();

            Timer.Tick += new EventHandler(Timer_Click);

            Timer.Interval = new TimeSpan(0, 0, 1);

            Timer.Start();
            #endregion
        }
        #region RealTime Clock
        public void Timer_Click(object sender, EventArgs e)
        {
            DateTime d;
            d = DateTime.Now;
            _currentTime = string.Format("{0}:{1}:{2}", d.Hour.ToString("00"), d.Minute.ToString("00"), d.Second.ToString("00"));
        }
        #endregion

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<Label Grid.Column="4" HorizontalAlignment="Right" Name="Clock" Foreground="WhiteSmoke" Opacity="0.7" VerticalAlignment="Center" Content="{Binding currentTime}" />
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public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        MainPageViewModel mvm = new MainPageViewModel();
        this.DataContext = mvm;
    }
}