you could use timespans, then you'd only need 1 timer

vb.net Code:
  1. Public Class Form1
  2.  
  3.     Dim t1 As New TimeSpan(0, 0, 0)
  4.     Dim t2 As New TimeSpan(8, 0, 0)
  5.     Dim t3 As New TimeSpan(16, 0, 0)
  6.  
  7.     Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
  8.         Dim timeNow As New TimeSpan(Now.Hour, Now.Minute, Now.Second)
  9.         If timeNow > t1 And timeNow < t2 Then
  10.             'do something
  11.         ElseIf timeNow > t2 And timeNow < t3 Then
  12.             'do something
  13.         ElseIf timeNow > t3 And timeNow < New TimeSpan(24, 0, 0) Then
  14.             'do something
  15.         End If
  16.     End Sub
  17.  
  18. end class