SUNDAY LETTER. 



express a day of the week one day later than that which it 

 expressed before the 29th February, and the same will conse- 

 quently be true of all the other letters. Thus, if the 22nd 

 February, to which D is annexed, were Monday, all the other 

 days, from 1st January to 28th February, to which D is annexed, 

 would also be Mondays, and consequently the 28th February, to 

 which c is annexed, must be Sunday, and therefore the 29th, to 

 which no letter is annexed, must be Monday, and therefore 1st 

 March, to which D is annexed, must be Tuesday, and all the suc- 

 ceeding days, to the end of the year, to which D is annexed, must 

 be Tuesdays. Thus, in a leap year, if D express Mondays before 

 the 29th February, it will express Tuesdays after that day, 

 and, in general, each letter after the 29th February, will express 

 the day of the week which succeeds that which is expressed before 

 the 29th February. 



It follows, therefore, that the Sunday letter in a leap year after 

 the 29th February, is the Saturday letter before it, and is, con- 

 sequently, the letter of the alphabet which precedes the Sunday 

 letter at the beginning of the year. Thus, if the Sunday letter 

 before 29th February be c, the Sunday letter after it will be B, if 

 D it will be c, and so on. If the Sunday letter before 29th 

 February be A, it will be G after it. 



A leap year, therefore, has two Sunday letters, the first 

 applicable to the part before, and the other to the part after, the 

 29th February. 



44. It has been supposed that the birth of Christ took place on 

 the Sabbath of the Jews, and consequently on the day now called 

 Saturday. Since 1st January is the seventh succeeding day, it 

 follows that the first day of the first year of the Christian era was 

 Saturday, and consequently the Sunday letter of the year 1 A.D. 

 was B. 



45. Since a common year consists of 52 weeks and one day, it 

 follows that the first and last day of such a year will fall upon the 

 same day of the week, and that the first seven days of the next 

 year will fall upon the week days which immediately succeed 

 those upon which they fell in the preceding year. This will 

 supply an easy rule, by which, when the Sunday letter of any 

 year is known, those of all succeeding years may be at once found 

 without calculation. 



Let us suppose that the 1st January, in a certain year, is 

 Sunday. The Sunday letter will then be A for that year. The 

 year being supposed to be a common year, its last day will also be 

 Sunday, and therefore the first day of the next year will be 

 Monday, and the seventh, Sunday. The Sunday letter of that 

 year will then be o. 



