What is the test the main character will use to determine the truth of where he is?

In Chapter Two, Hank meets a young page named Clarence who tells him that he is in King Arthur's court and that the year is 528. Hank realizes that something has gone terribly wrong, but his reason refuses to believe that he has been transposed 1300 years before his birth. He knows that if what Clarence says is true, there should be a total eclipse of the sun in exactly two days time, and he resolves to wait out that period to test the truth.