WPF Graph - format of AxisDateTime

Hello.

I am using NI Graphs in my WPF application. The graphs are binded to ChartCollection <TimeSpan, double>. Here is my graph XAML code and the picture:

<ni:Graph x:Name="graph_temperatures" PreferIndexData="False" RenderMode="Raster">
     <ni:Graph.Axes>
          <ni:AxisDateTime Orientation="Horizontal"/>
          <ni:AxisDouble Label="Temperature [°C]" Orientation="Vertical" Range="0, 100, System.Double"/>
     </ni:Graph.Axes>

</ni:Graph>

And I would like to change default format of datetime axis to be like this: "hh:mm:ss". How can I easily do it please?

Thank you for support.

Jakub