Maybe the 13th Century? I remember reading that the Basque were able to sail as far as Newfoundland for fishing and did so centuries before Columbus arrived
As LampLighters said, this is just a possibility that many seem to have accepted as a fact so much because it gets repeated so much as an interesting possibility. Even if it is true (which, again, is not even close to certain) no credible scholar to my knowledge has proposed such voyages took place as early as the 13th century.
It seems to be a fairly widespread opinion, with some textual evidence but, far as I know, no archeological proof or even suggestion. But the same was true of the Norse in Vinland for a long time.
Except the Norse claim has infinitely more textual evidence. They had historically known colonies right next door to the Americas, and in Iceland wrote pretty extensively of how they found a place next door. The only textual evidence for Basque discovery prior to 1492 is that sometimes a phantom island called "Codfish" appeared on maps -named, I might add, for the Portugese word for codfish, never the Basque. The two situations are not remotely comparable.