Prehistory is the period of time before recorded history. Prehistoric events can be dated, but not on the basis of records kept at the time when they took place. Rather, they can be dated on the basis of models developed by natural and social sciences. Posthistory is the period of time after recorded history. Posthistoric events can be predicted on the basis of models developed by natural and social sciences, as well. Just as it took a certain amount of time for historic records to be developed, it will take a certain amount of time for historic records to fall into disuse. In broad terms, the historic period coincides with the current interglacial period, which is coming to an end. Like previous interglacial periods, it will end with a rapid drop of temperature on earth. Posthistory will thus arrive quite rapidly. Broadly speaking, it can be expected to follow social development leading up to the historic period, albeit in reverse. Prehistory is therefore a useful guide for posthistory. However, that guide will disappear with the end of the historic period. In other words, the best time for the study of posthistory is now.