WEEKDAY, a C library which can determine the day of the week corresponding to a given date.
The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.
WEEKDAY is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version and a Python version.
ANALEMMA, a C program which evaluates the equation of time, a formula for the difference between the uniform 24 hour day and the actual position of the sun, by Brian Tung.
DATES, a dataset directory which contains lists of dates in various calendar systems.
DOOMSDAY, a C library 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 C library which supplies test values of various mathematical functions.