timeupdown

 <Style x:Key="timeUpDown" TargetType="tookit:TimeUpDown">
            <Setter Property="Height" Value="25"></Setter>
            <Setter Property="MinWidth"  Value="75"></Setter>
            <Setter Property="Value"  Value="12:00:59"></Setter>//无用，不能再这里设
            <Setter Property="Format" Value="Long"></Setter>
            <Setter Property="HorizontalAlignment" Value="Left"></Setter>
            <Setter Property="VerticalAlignment" Value="Center"></Setter>           
  </Style>

应该这样写，其中Value="12:00:59" 必须有

 <tookit:TimeUpDown x:Name="UseTimeStart" Grid.Row="0" Grid.Column="4" Value="12:00:59" Style="{StaticResource timeUpDown}" ></tookit:TimeUpDown>