COMMON THINGS THE ALMANACK. 



attended with future consequences so important, invested with no 

 circumstances which could lead to its having been recorded in the 

 public annals, does not at all affect chronology ; since whatever 

 may have been the actual day of Christ's birth, that which 

 connects the Christian with the ancient chronology is the first day 

 of the year 754 of Rome. 



To convert any year A.D. into the corresponding year of Rome, 

 it is only necessary therefore to add 753 to it. Thus the year 

 1 A.D. was the year 754 of Rome, the year 20 A.D. was the year 

 773 of Rome, and so on. 



It will be observed that the first year of the Christian era is 

 not, as might be imagined, that of the birth of Christ, but the 

 following year. It is the year in which, according to the researches 

 of Dionysius Exiguus, Christ completed his first year. 



8. Since, according to the Christian chronology, time is counted 

 thus prospectively forward from the birth of Christ, the year after 

 that event being taken as the first year of the series, it might by 

 analogy be presumed that in counting time retrospectively the 

 year before the same event would be taken as the first year of the 

 backward series. Thus while the year after that of the birth of 

 Christ is 1 A.D., the year before that of the birth of Christ would 

 be the year 1 B.C., and consequently that the year itself in which 

 Christ was born would be either A.D. or B.C. indifferently. 

 By such a mode of expressing dates, the interval between any day 

 in any year A.D., and the corresponding day in another year B.C., 

 would be found by adding together the numbers expressing the 

 years. Thus the interval between 1st July, 1 A.D., and 1st July, 

 B.C., was 1 year; the interval between 1st July, 1 A.D., and 

 1st July, 1 B.C., was 2 years; the interval between 1st July, 15 

 A.D. and 1st July, 14 B.C. was 29 years, and so on. 



And this is, accordingly, the method of expressing dates which 

 astronomers use. It is, however, unfortunately, not that adopted 

 by historians and chronologists. According to these the year 

 753 of Rome, in which Christ is supposed to have been born, is 

 the year 1 B.C., and consequently all their dates B.C. exceed the 

 corresponding dates of astronomers by 1. Thus the year which 

 astronomers call 500 B.C., historians call 501 B.C. 



To find, therefore, the interval between any day in a year A.D. 

 and the corresponding day in any year B.C. when the historical 

 dates are used, it will be necessary to add together the two dates 

 and subtract 1 from their sum. 



9. Historical events are often referred to by stating that they 

 occurred in such or such a century. Now one might well suppose 

 that there could arise no obscurity or confusion in the use of such 

 a term, yet it is notorious that after the year 1800, questions were 



