The example I posted used a format of "HH"; it is possible you just have to change that to "HH:mm". It looks by the screen shot like you are using a TimeSlotInterval of 'TenMinutes', but I am at a loss as to how you got the text to appear for each slot (by default, it only appears for the first slot in the hour section). If you could illuminate on that point we can try to help.

using Infragistics.Win;
using Infragistics.Win.UltraWinSchedule;
using nsDayView = Infragistics.Win.UltraWinSchedule.DayView;

this.dayView.CreationFilter = new TimeSlotDecriptorCreationFilter( "HH" );

#region TimeSlotDecriptorCreationFilter
/// <summary>
/// Provides a way to add labels for DayView's TimeSlotUIElements
/// </summary>
public class TimeSlotDecriptorCreationFilter : IUIElementCreationFilter
{
    private string format = null;
    public TimeSlotDecriptorCreationFilter( string format )
    {
        this.format = format;
    }

    #region IUIElementCreationFilter interface implementation

    void IUIElementCreationFilter.AfterCreateChildElements(UIElement parent)
    {
        nsDayView.HourUIElement hourElement = parent as nsDayView.HourUIElement;
        if ( hourElement != null )
        {
            nsDayView.TimeSlotDescriptorUIElement descriptorElement =
                hourElement.GetAncestor( typeof(nsDayView.TimeSlotDescriptorUIElement) )
                as nsDayView.TimeSlotDescriptorUIElement;

            TimeSlot slot = descriptorElement.FirstTimeSlot;

            hourElement.Text = slot.StartTime.ToString(this.format);
        }

        nsDayView.TimeSlotDescriptorUIElement timeSlotDescriptorElement = parent as nsDayView.TimeSlotDescriptorUIElement;
        if ( timeSlotDescriptorElement != null )
        {
            nsDayView.MinuteUIElement minuteElement =
                timeSlotDescriptorElement.GetDescendant( typeof(nsDayView.MinuteUIElement) )
                as nsDayView.MinuteUIElement;

            if ( minuteElement != null )
                minuteElement.Text = "00";
        }

    }

    bool IUIElementCreationFilter.BeforeCreateChildElements(UIElement parent)
    {
        return false;
    }

    #endregion IUIElementCreationFilter interface implementation
}
#endregion TimeSlotDecriptorCreationFilter

Can you point me to an example of setting the TimeSlotDescriptor "time format" to 24 Hour time/Military Time

eg: 1:00 pm = 13:00

Cheers

Aaron