Created Unassigned: DateTimeUpDown control not working with unknown time format [22355]

I am using DateTimeUpDown control from assembly "Xceed.Wpf.Toolkit". When I change my date time setting

Change date and time settings ---> Change date and time ----> Change Calendar settings ---> Select time tab ----> In long time combo box, type h m t s, even my time in DateTimeUpDown changes.

When i run the application, the control giving 19 10 45 as output, but required output is 19:10:45 because i have specified FormatString for the control. The control is not giving expected output. How could be done this?


<Window x:Class="DefaultTimeFormat.DateTimeUpDown"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:Ext="clr-namespace:Xceed.Wpf.Toolkit;assembly=Xceed.Wpf.Toolkit"
xmlns:local="clr-namespace:DefaultTimeFormat"
Title="DateTimeUpDown" Height="300" Width="300">
<Grid>
<Ext:DateTimeUpDown Height="30" Format="Custom" FormatString="HH:mm:ss" x:Name="T1" />
</Grid>
</Window>