How to show the score at the top left of the screen?

Mine was not working. Please help me.

draw = function()
  screen.clear()
  local textPixels = screen.textWidth( system.time(), 20 ) 
  screen.drawText( system.time(), -screen.width/2 + textPixels / 2, screen.height/2 - 10, 20, "orange" )
end