doomsday

doomsday, a FORTRAN77 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.

Licensing:

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Languages:

doomsday 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.

Related Data and Programs:

doomsday_test

analemma, a FORTRAN77 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, creating data that can be plotted by gnuplot, based on a C program by Brian Tung.

calendar_nyt, a FORTRAN90 library 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 and Nachum Dershowitz

CALPAK, a FORTRAN90 library which makes various calendar calculations;

DATES, a dataset directory which contains lists of dates in various calendar systems.

WEEKDAY, a FORTRAN77 library which determines the day of the week for a given day.

Reference:

1. Lewis Carroll (Charles Dodgson),
   To Find the Day of the Week for Any Given Date,
   Nature, 31 March 1887.
2. John Conway,
   Tomorrow is the Day After Doomsday,
   Eureka,
   Volume 36, October 1973, pages 28-31.
3. Gary Meisters,
   Lewis Carroll's Day-of-the-Week Algorithm,
   Math Horizons,
   November 2002, pages 24-25.

Source Code:

• doomsday.f, the source code.
• doomsday.sh, BASH commands to compile the source code.