Hello David Sandor,
Unfortunately, this scenario is not supported in the current version of the control. Basically, RadTimeBar changes the collection of the interval items dynamically, based on a couple of conditions such as available space, font size, interval types in the Intervals collection, visible period, etc.
Since your case is very specific, I am not quite sure I can offer you a workaround either. The only thing that I can suggest, is to try to create your custom SelectionThumb control that implements a specific coercing mechanism that fits your requirements and use it in the place of the default one in the template of the timeBar control. This, however, would require major re-templating of the timeBar control and the effort to create a custom SelectionThumb control.
the Telerik team