weekday_zeller, a Python code which uses Zeller's congruence to determine the day of the week corresponding to a given date, such as 13 July 1989, Gregorian calendar, ... which was a Thursday.


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


weekday_zeller is available in a MATLAB version and a Python version.

Related Data and Programs:

calpak, a Python code which makes various calendar calculations;

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

doomsday, a Python 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.

weekday, a Python code which determines the day of the week for a given day.


  1. Nick Berry,
    Zeller's Congruence,
  2. J R Stockton,
    The Calendrical Works of Rektor Chr. Zeller: The Day-of-Week and Easter Formulae.

Source Code:

Last revised on 06 November 2019.