You can have tooltips for all case of positions in the Calendar Control.

 

Personally, I use 3 types of tooltip in the Calendar Control:

You can set tooltip in the MouseMove Event :

 

 

Private Sub Calendar_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
Dim HitTest As CalendarHitTestInfo
    
    Set HitTest = Calendar.ActiveView.HitTest
    If Not HitTest.ViewEvent Is Nothing Then
        If HitTest.ViewEvent.Event.AllDayEvent Then
            Calendar.ToolTipText = HitTest.ViewEvent.Event.Subject
        Else
            Calendar.ToolTipText = ExtractTime(HitTest.ViewEvent.Event.StartTime) & "-" & ExtractTime(HitTest.ViewEvent.Event.EndTime) & " " & HitTest.ViewEvent.Event.Subject
        End If
    Else
        Calendar.ToolTipText = ExtractTime(HitTest.HitDateTime)
    End If
End Sub

 

' *** A function to extract the time from the date event

Private Function ExtractTime(Dt As Date) As String
    ExtractTime = Format(Dt, "hh:nn")
End Function

 

Hope it will help you