Use this Sub I wrote.

It will scan ALL Owners DayOfWeekSettings to determine how many hours need to be displayed in the Dayview.

Eg: If the earliest an owner begins work is 7am then it will display 1 1/2 hours before 7, making the first timeslot = 5:30am

And if the latest any particular owner ends work it will display 1/2 an hour after that. So if latest an owner finishes is 5pm then it timeslots upto 5:30pm will be visible.

    Private Overloads Sub SetLogicalDayDuration(ByVal cinfo As UltraCalendarInfo)

        Dim LowestOpenTime As DateTime = New DateTime(2000, 1, 1, 23, 59, 59)
        Dim HighestCloseTime As DateTime = New DateTime(2000, 1, 1, 0, 0, 0)
        Dim OpenTimeResult As DateTime
        Dim CloseTimeResult As DateTime

        Try

            For Each own As Owner In cinfo.Owners
                If own Is cinfo.Owners.UnassignedOwner Then Continue For
                For Each DyOfWSetting As DayOfWeekSettings In own.DayOfWeekSettings
                    If DyOfWSetting.WorkDayStartTime.TimeOfDay = New TimeSpan(0, 0, 0) Then Continue For
                    If LowestOpenTime.TimeOfDay > DyOfWSetting.WorkDayStartTime.TimeOfDay Then
                        LowestOpenTime = DyOfWSetting.WorkDayStartTime
                    End If

                    If HighestCloseTime.TimeOfDay < DyOfWSetting.WorkDayEndTime.TimeOfDay Then
                        HighestCloseTime = DyOfWSetting.WorkDayEndTime
                    End If
                Next
            Next

'Make Sure Lowest and Highest Times are not less than or greater than midnight (00:00 hours)
            If New TimeSpan(LowestOpenTime.Hour - 1, 30, 0) < New TimeSpan(0, 0, 0) Then
                cinfo.LogicalDayOffset = New TimeSpan(0, 0, 0)
            Else
                cinfo.LogicalDayOffset = New TimeSpan(LowestOpenTime.Hour - 1, 30, 0)
            End If

            If New TimeSpan(HighestCloseTime.Hour - cinfo.LogicalDayOffset.TotalHours + 0, 30, 0) > New TimeSpan(24, 0, 0) Then
                cinfo.LogicalDayDuration = New TimeSpan(23, 59, 59)
            Else
                cinfo.LogicalDayDuration = New TimeSpan(HighestCloseTime.Hour - (cinfo.LogicalDayOffset.TotalHours - 1) + 0, 30, 0)
            End If


'Set the CalendarInfo Properties with Result
            cinfo.LogicalDayDuration = New TimeSpan(CloseTimeResult.Hour, CloseTimeResult.Minute - 30, 0)
            cinfo.LogicalDayOffset = New TimeSpan(OpenTimeResult.Hour - 0, -30, 0)
        Catch ex As Exception
            LogPrint("Error - frmAppointments:" & ex.TargetSite.ToString & ": " & ex.Message.ToString, 5)
        End Try
    End Sub

If this is all to complicated and you don't want this and you just want to statically set the time period shown then do the following:

calInfo.LogicalDayOffset = New Timespan(9,0,0)
calinfo.LogicalDayDuration = New Timespan(8,0,0)

This will give you an 8 hour day starting at 9am and ending at 5pm