Civilization has been progressing on Erde at about the same rate as on Earth; the time frame for the adventures is roughly equivalent to the end of our Classical era – just before the fall of the Roman Empire. In-game, it is Imperial Year 586: if you think of IY as C.E., it might be a helpful guide for your imagination, although there is no meaningful direct correspondence.
The face of Erde has changed over the past six millennia as the territory and hegemony of the various civilizations has ebbed and flowed. On Erde, seven great civilizations have arisen, incorporating what had been scattered tribes, clans, and communities into seven distinct societies. The Atalantans are perhaps the oldest civilization; the origins of this cultural giant are shrouded in myth. The Haan are another ancient civilization, with perhaps the longest continuous culture on Erde. The Bayakans are island peoples but have been on the mainland since antiquity. The Attikans, Rassenans, and Picts all have their origins in the small tribal communities of central Erde but have grown to expand their borders, their hegemony, and their influence. The Hirokoa from moonward Erde are the most recent member of the family, having grown and prospered in relative isolation for much of Erde’s recorded history.
The following maps show the development of Erdan civilizations.