function drawWeekGrid( bitmap )

  // week hilights
  for x=0, bitmap.width, 140 do
    bitmap.rect( x, 0, x+70, bitmap.height, Color(250,250,250), Color(250,250,250) )
  end

  // dense light grid
  for x=0, bitmap.width, 10 do
    bitmap.line( x, 0, x, bitmap.height, Color(240,240,240) )
  end
  for y=bitmap.height-1, 0, -10 do
    bitmap.line( 0, y, bitmap.width, y, Color(240,240,240) )
  end
  
  // sparse dark grid
  for x=0, bitmap.width, 70 do
    bitmap.line( x, 0, x, bitmap.height, Color(120,120,120) )
  end
  for y=bitmap.height-1, 0, -100 do
    bitmap.line( 0, y, bitmap.width, y, Color(120,120,120) )
  end

end