@Dinsdale
That is a very arbitrary and US-centric definition!
No, because wasn't "Columbus discovers the United States". It was the opening of the regular exchange of goods and culture between Europe and the Americas, which affected Europe pretty significantly, though maybe not so much as it affected the Americas.
There's an awful lot of stuff that was simply unknown in Europe before that, because it originated in the New World. There were no tomatoes, no potatoes, no syphilis, no tobacco... they didn't have those turkey legs people love gnawing on at RenFaires...
And that's not to mention what the sudden introduction of two new continents to be claimed did to European politics...
I've been in the SCA for decades. Our period is officially "pre-17th century", so it ends at the stroke of midnight on December 31st, 1600. I've long held, though, that it should be October 12th, 1492, just because it would put an end to a lot of very silly, "Oh, well, they could have had..."
(They'd probably just start going, "Oh, well, the Vikings could have brought it back from Vinland," though.)