Consider the three famous eclipses of Thucydides - 5th century B.C.("History of the Peloponnesian War": Bks.ii, 27-28; iv,51-52; vii,18-19,50). They can be dated using modern methods. There are only two exact astronomical solutions: the first solution is August 2, 1133 A.D., March 20, 1140 A.D., and August 28, 1151 A.D., whereas the second is August 22, 1039 A.D., April 9, 1046 A.D., and September 15, 1057 A.D. This example is not unique.