OFFSET
1,1
COMMENTS
Friday the thirteenth appears more often than any other day.
In the cycle of 400 Gregorian years there are 303 regular years with 365 days, and 97 leap years with 366 days, so the total number of days is 303*365 + 97*366 = 146097, which is divisible by 7. - Amiram Eldar, Apr 29 2022
REFERENCES
Alfred S. Posamentier, Math Charmers, Tantalizing Tidbits for the Mind, Prometheus Books, NY, 2003, page 230.
LINKS
E. G. Richards, Mapping Time, The Calendar and its History, Oxford University Press, Great Clarendon Street, Oxford OX2 6DP, Reprinted 1999 (with corrections).
Wikipedia, Gregorian calendar
MATHEMATICA
(* first do *) Needs["Miscellaneous`Calendar`"] (* then *) t = Flatten[ Table[ DayOfWeek[{y, m, 13}], {y, 2000, 2399}, {m, 12}]]; d = Table[ DayOfWeek[{2006, 1, d}], {d, 1, 7}]; Table[ Count[t, d[[n]]], {n, 1, 7}]
CROSSREFS
KEYWORD
fini,full,nonn,dumb
AUTHOR
Robert G. Wilson v, Jan 28 2005
STATUS
approved