Footnote

b In computing the total years from any B.C. to any A.D. date one must not only add the two figures together but also subtract one year because of there not being any year A.D. or B.C. 0. Thus from 1 B.C. to A.D. 1 is not two years but only one year. It therefore follows that 420 years back form the destruction of the temple A.D. 70 reaches to 351 B.C. not 350 B.C. It is very likely that some Jewish chronologists overlooked this fact.