very nice ideas from sean!
Let me add on by trying to generalize and re-organize the suggestion a little so that it becomes a little more dynamic:
Instead of a fixed sequence of "ages", a historic "period" (as opposed to just a a fixed/ordered stage in world generation) can a period of some constance in the whole world of within a substantial part of the world. Period transitions are when great changes/events disrupts this constance therefore bringing significant changes to region or even the whole world.
An "Age" could be a period that becomes long enough. (we don't call a 20 year period an Age. But 200 years will seem more acceptable). In that respect, "Ages" could be identified and named (by scholars a long time after that) after the historic periods are identified and generated.
possible period triggers and features:
Do note that they may overlap and may also be combined (e.g. An Age could be of both Empire-type and peace-type if say an empire dominates the world and brought about a long period of peace)
-Change of the rules of Reality. Could be deity related. E.g. Introduction/Death of magic.
-Birth/Death of a civilization/race. e.g. an "ancient" Age of myths could be where fantastic and majestic creatures lived side by side. The extinction/disappearances(escaped from this world) of many such fantastic races may mark te end of such an Age.
-Long periods of war/peace. When there's long time peace, it would become something like Golden Age, where focus is not on war/weapons but on arts and sciences (and perhaps magic). On the other hand, a long period of widespread war and strife could be named as an Age with keywords like Blood/Chaos/Dark.
-Gain/Loss of dominance (empire). e.g. when a civizillization gain dominance (high population, huge domain, forcing the othe civillizations to retreat to corners of the empire/into deep forests/high mountains/deep seas) for a substantial time, it could be named an (empire-type) Age after the Empre's name. The fall of the empire (which could lead to a period of conflict) markes the end of the dominance.
-Cultural/Technological advancements. e.g. Invention or discovery that revolutionizes some cultural aspects and the whole world (e.g. invention of saddle obseleted chariots that once dominated the ancient battlefields and drastically changes the rules of battle which indirectly could cause rapid civilizations risings and fallings)
-Natural/Unnatural disasters. e.g. widespread plagues that kills millions/wide out civillizations. or the cliche "somebody left a gate to hell open" type that unleashes outsider/demonic enemies that attack all (and maybe force old enemies to form alliances against common enemy). Great earthquake that changes the whole continent's features, meteor strikes that create great indoor seas, great flood that permanently submerges large spans of land.
Would be interesting if the events during world generation can be analyzed and have the periods marked out, and then have the longer periods/sequences of periods be made an "Age" and given a approrpiate (but still dynamic) name.
(feel free to add on if something cannot be classified by the above)
E.g. Sample historical accounts of historic periods and ages.
"It is in the year 401 that a humble peasant from the human town of Two Rivers takes up weapon to protect his kin, and with his incredible charisma, gathered the people of the town, then the people of the nearby town, and finally the humans of the whole region under one banner. The banner of the White Hawk, symbolizing the freedom that the humans sought, freedom from the war, death and slavery that is very definition of the Age of Chaos. Once thought to be the weakest among the races since the Age of Myth, the humans became a mighty nation of determined people, and the once-peasant became the greatest warrior-king in the human histories. After 200 years of determination, innovation, incredible skills and perhaps a substantial dash of luck, the nation of White Hawk finally broke the last Horde of the Orcs. The remaints of the once proud Horde were scattered as they escaped into the mountains, and their once mighty civillization is doomed, never to be rebuilt. Thus finally ended the Age of Chaos, and begun a new age, the Age of the Empire..."
"Year 735, The once mighty Empire had become rotten to the core. The falling of the last of the line of the ruling family to poison was the last straw, that marks the begining of a rapid disintegration of the 300-year-old Empire, as nobles rebeled and peasant rioted and once loyal vassal nations declared their independence. Thus end the Age of the Empire and began the period of Gray Unrest..."
"Year 950. The dwarves which had been hiding in seclusion among the mountains since the Age of Chaos had finally emerged and made contact with the humans of the West Ridge... Soon after, the elves remerged as well... With the signing of peace treaties, emergence of trade, and exchanges in the arts and cultures, history entered the Golden Age, an Age of Art and Learning, as well as Trade and Opportunities."
Edit: fixed the more serious typos. If there are still any left, pretend you did not see.
[ January 15, 2008: Message edited by: sphr ]