Diablo is followed shortly by Diablo II and Diablo III comes 20 years after that, but how old is the world of Sanctuary as a whole?
According to some timelines, III occurs in 1285, but did the counting of the years start with the creation of Sanctuary or the winking into existence of the High Heavens/Burning Hells? I figure as angels and demons aren't mortal, they don't really count the years as us mortals do, but I haven't found anything that says this outright.