This period was "the thirteenth year of Henry VII." The thirteenth year of Henry began on the twenty-second of August, 1497, and ended in 1498.

On the third of February, 1498, Henry VII granted permission to Cabot to take six English ships "to the lands and islands recently found by the said Cabot, in the name of the king and by his orders." Strictly speaking, this would mean that the mainland had then been discovered; but it is impossible to establish the claim of England on these terms.
What is, however, more to the point, is a letter from Pasqualigo, a Venetian merchant, who says, writing to Venice, on the twenty-third of August, 1497, that Cabot had discovered the mainland at seven hundred leagues to the west, and had sailed along it for a coast of three hundred leagues.

He says the voyage was three months in length.

It was made, then, between May and August, 1497.

The evidence of this letter seems to show that the mainland of North America was really first discovered by Cabot.