“One of the more sophisticated aspects of Trollish culture is their traditional view of time. As the past, where we have been, can be ‘seen’, whereas the future, where we are going, lies in front of us, they logically conclude we are going through time facing backwards. Also, since they are a nocturnal race, the trollish equivalent of the ‘Dawn of Time’ is the ‘Sunset of Time.'”
–Wikipedia entry on “Troll (Discworld)”