3 billion years
The primary D&D 5e world in which I operate for my players. It is a Realistic, lower fantasy world in which politics, crime, and the world at large is as dangerous as a tribe of cave goblins. Where resting takes a more realistic time, and a Cleric is akin to Jesus. Where a single magic user can turn the tide of an entire battle simply for the sake they can cast magic. Depending on the region, one may find where the sole Dragonborn live within their hidden settlement, or might find a country filled with magical advancements, or even yet another on the verge of technological breakthroughs.
Vallina is a Medieval-eqsue world in which the diparity in countries is as real as it was before - where it generally took time to get information across places, unless they had a wizard to help. Where technological advancements were a close guarded secrets. The world is a living, breathing place in which everyone's actions have consequences, both players and NPCs alike.