About the RightToLeft, as I said Infragistics has ignored that as far as I know, but I tried today to create my first creation filter and looks like it is very simple to do it:

This post is a little old. But I thought there might be lots of Arabic, Persian and Hebrew users who would want to make the DayView right to left. I did it like this:

public partial class Form1: Form, Infragistics.Win.IUIElementCreationFilter
    {

        private void Form1_Load(object sender, EventArgs e)
        {
            ultraDayView1.CreationFilter=this;
        }

        public void AfterCreateChildElements(UIElement parent)
        {

            // if the mainUIElement of the DayView is being added
            if (parent is MainUIElement)
            {

                // ChildElements 1-to-8 are the 7 days of the week,
                // invert their positions (1 to 7, 2 to 5, 3 to 4)
                for (int i = 1; i < 4; i++)
                {
                    GroupUIElement col1 = (GroupUIElement)parent.ChildElements[i];
                    GroupUIElement col2 = (GroupUIElement)parent.ChildElements[8-i];
                    Rectangle rect1 = ((GroupUIElement)parent.ChildElements[i]).Rect;
                    Rectangle rect2 = ((GroupUIElement)parent.ChildElements[8-i]).Rect;
                    col1.Rect = rect2;
                    col2.Rect = rect1;
                }
            }

        }
        public bool BeforeCreateChildElements(UIElement parent)
        {
            return false;
        }

     }

Note that this only works if DayView is displaying 7 days of the week. For 5 days or any other number, you should make a little change to the numbers in the "for" clause (you should use something else instead of 4 & 8).

And please note that after doing this, a lot things won't work. like dragging appointments, or changing the days with keyboard arrows, or resizing day columns. So you better disable or rewrite them.