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public partial class TimePicker : UserControl, INotifyPropertyChanged
{
   [...]
   DateTime _Time = DateTime.Now;
   [Description("The time displayed by the timePicker"), Category("Time Control")]
        public DateTime Time
        {
            get { return (DateTime)GetValue(TimeProperty); }
            set {
                  if(_Time.Equals(value))
                    return;

                  if (value != null)
                      _Time = value;
                  else
                      _Time = new DateTime(2014, 1, 1, 0, 0, 0); //DateTime.Now;
                  
                  OnPropertyChanged("Time");
                  OnPropertyChanged("TimeHour");
                  OnPropertyChanged("TimeMinute");
                  OnPropertyChanged("TimeSecond");
                  SetValue(TimeProperty, Time); }
        }
   public static readonly DependencyProperty TimeProperty = DependencyProperty.Register("Time", typeof(DateTime), typeof(TimePicker)); 
   [...]
}                    

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public string TimeHour
{
  get
  {
    return Time.Hour.ToString("00");
  }
  set
  {
    int hour;
    if (int.TryParse(value, out hour))
    {
       if (hour >= 24)
         Time = new DateTime(Time.Year, Time.Month, Time.Day, 0, Time.Minute, Time.Second);
       else if (hour < 0)
         Time = new DateTime(Time.Year, Time.Month, Time.Day, 0, Time.Minute, Time.Second);
       else
         Time = new DateTime(Time.Year, Time.Month, Time.Day, hour, Time.Minute, Time.Second);
    }
  }
}                    

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<wpfCon:TimePicker Time="{Binding LeadingDateTime}"/>
<DatePicker SelectedDate="{Binding LeadingDateTime}"/>