i am not 100 % sure if i understand you corrently.
I am working on a 24 hour timscale (German UI) an i use this routine to set the working hours.
Private Sub SetWorkingHours()
Dim istart, iend As Integer
istart = My.Settings.wtStart
iend = My.Settings.wtEnd
Dim interval As New TimeSpan(istart, 0, 0)
Dim interval2 As New TimeSpan(iend, 0, 0)
Dim timeInterval As New TimeInterval(interval, interval2)
CType(Me.rsTracks.ActiveView, SchedulerDayViewBase).WorkTime = timeInterval
rsTracks.GetDayView.RulerStartScale = istart
rsTracks.GetDayView.RulerEndScale = iend
.Worktime will set the range you can give a different properties like background color to seperate then visual from others times.
.RulerStartScale and .RulerEndScale set the outer scroll end for you time ruler in dayview.
I don't know if it is possible to change the direction of the ruler from ascending (00:00 to 23:59) to descending (23:59 - 00:00).
Please make more clear what kind of ruler you want.