weekday, a FORTRAN90 code which determines the day of the week corresponding to a given date; for instance, the battle of Hastings, on 14 October 1066 (Julian Calendar!), was a Saturday.
The computer code and data files described and made available on this web page are distributed under the MIT license
weekday is available in a C version and a C++ version and a Fortran90 version and a MATLAB version and an Octave version and a Python version.
analemma, a FORTRAN90 code which evaluates the equation of time, a formula for the difference between the uniform 24 hour day and the actual position of the sun, based on a program by Brian Tung.
calendar_nyt, a FORTRAN90 code which shows the correspondence between dates and the New York Times volume and issue number;
calendar_rd, a C++ program which computes the representation of a given date in a number of calendrical systems, by Edward Reingold, Nachum Dershowitz
calpak, a FORTRAN90 code which makes various calendar calculations;
DATES, a dataset directory which contains lists of dates in various calendar systems.
doomsday, a FORTRAN90 code which is given the year, month and day of a date, and uses John Conway's doomsday algorithm to determine the corresponding day of the week.
test_values, a FORTRAN90 code which supplies test values of various mathematical functions.