DOOMSDAY is a Python 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.
The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.
DOOMSDAY is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version and a Python version.
DATES, a dataset directory which contains lists of dates in various calendar systems.
You can go up one level to the Python source codes.