38 BULLETIN OP THE 



January 1 May 2 September 6 



rebriiary 4 June 5 October 1 



March 4 July or T November 4 



April or 7 August 3 December 6. 



d is the day of the month under consideration; Yn, the largest 



multiple of 7 contained in k-\-'m -\- d ; c, the hundreds of the 



year ; y, the excess above the hundreds ; and r, the remainder 



after dividing c by 4. 



The general formula may be read thus: — 

 To the year number add the month number and the day of the 

 month, and the excess over the largest contained multiple of 1 is 

 the number of the day of the week. 



For years B. C, subtract the given year less one from 2800, 

 or some multiple of 2800, and use the above expression of k for 

 either old or new style. 



Mr. Frisby and Mr. Gill referred to instances where dates 

 were given both in the old and new styles, the latter stating 

 that this was usually done in the publications of Russian scien- 

 tific societies. 



Mr. ScHOTT called attention to the difference of a day in 

 American and Russian dates in Alaska, the latter being in 

 advance, the American Sunday corresponding to the Russian 

 Monday. 



Mr. W. B. Taylor gave an account of 



A CALENDAR PROPOSED BY A PERSIAN ASTRONOMER IN 1019. 



(abstract.) 



There is one calendar scheme not included, I believe, in Mr. 

 Elliot's formulae, which appears to me of sufficient interest to 

 deserve a notice. More than five hundred years before the adop- 

 tion of the calendar of Gregory, a Persian astronomer, Omar 

 Cheyam, one of a commission appointed by the Sultan of Kho- 

 rassan to reform the calendar, proposed (A. D. 1079) a very 

 simple modification of the Roman or Julian system, by postpon- 

 ing for one year, every eighth Julian leap year, giving the con- 

 tinuous succession of seven quadrennial periods, followed by one 

 quinquennial period. That is to say, the leap year which by the 

 Julian calendar should take place on every 32d year was uni- 

 formly carried forward so as to fall on everv Sod year. This 

 delay by one year would in four such periods, or in 132 years, 



