POPE GREGORY'S TEN DAYS 263 



previously assigned to it ! At the same time, so that 

 three months of thirty-one days might not come together, 

 September and November were reduced to thirty days, and 

 thirty-one given to October and December. In order 

 to get everything into order and start fair Julius Caesar 

 restored the spring equinox to March 25th (Numa's date 

 for it, but really four days late). For this purpose he 

 ordered two extraordinary months, as well as Numa's 

 intercalary month Mercedonius, to be inserted in the year 

 47 B.C., giving that year in all 445 days. It was called 

 " the last year of confusion." January ist, forty-six years 

 before the birth of Christ and the 7o8th since the founda- 

 tion of the city, was the first day of " the first Julian year." 

 Although Julius Caesar's correction and his provisions 

 for keeping the " civil " year coincident with the astrono- 

 mical year were admirable, yet they were not perfect. His 

 astronomer, by name Sosigenes, did his best, but assumed 

 the astronomical year to be n min. 14 sec. longer than it 

 really is. In 400 years this amounts to an error of three 

 days. The increasing disagreement of the " civil " and 

 the " real " equinox was noticed by learned men in succes- 

 sive centuries. At last, in A.D. 1582, it was found that the 

 real astronomical equinox, which was supposed to occur on 

 March 25th, when Julius Caesar introduced his calendar 

 (not on March 2ist, as was later discovered to be the 

 fact), had retrograded towards the beginning of the civil 

 year, so that it coincided with March nth of the calendar. 

 In order to restore the equinox to its proper place 

 (March 2ist), Pope Gregory XIII directed ten days to be 

 suppressed in the calendar of that year and to prevent 

 things going wrong again it was enacted that leap-year 

 day shall not be reckoned in those centenary years which 

 are not multiples of 400. Thus Pope Gregory got rid 

 of three days out of the Julian calendar, or civil year, in 

 every 400 years, since 1600 was retained as a leap-year, 



