Series: Zellers Algorithm

It was my birthday this week so I got to thinking about one of my old Pascal Programs which was a program that used Zellers Algorithm or Congruence to calculate the day of the week from a given date. In this post all I wanted was to share my old Pascal program. In my next … Read more

When I started college in 1998, I was studying A-Level mathematics and was introduced to Zeller’s Algorithm. When I then started studying programming I though this would be a great algorithm to turn into a program(that program can be found here). I have been thinking about projects which I wish to put up on this … Read more

Now that we know that the algorithm works we can know build a solution We will start by adding code to perform the calculation for this we will need to import the Python math module so that we can use the built in floor function. We will also have to take into account the months … Read more

Something I am constantly wanting to do in a lot of programs is see if a value is in an array. For another function which I wish to write to add to the Zeller program this will come in handy. The basic algorithm looks like this: SET value TO RequiredValueSET array TO ArrayToSearchSET isIn TO … Read more

Another good function which would come in handy for Zeller is a function to make sure the date which was inputted is valid and display a message if the program has encountered an invalid date. For this function I will be using my inArray function which I wrote in a previous post. I will utilise … Read more

The next evolution of this project is to eventually create a graphical user interface(GUI). This is possible to do using Python. But, I want to use Java for this job so recreating the work I have already done in Java is the way to go. So what’s first. The first thing is to write the … Read more

I have just realised a mistake in my validDate Function. The mistake is that it only validates the day and not the month or year, i also realised that it would validate the day even if the day is zero so I need to fix this. It was only when I was creating the Java … Read more

With the updated Python function, comes an updated Java function, the code now looks like this, similar to the Python function there are two new checks and a final check that daysInMonth is not still zero: With this function working correctly, I can now continue with developing the GUI.

The Final step is to create the GUI, I have sketched out my plan by hand. My initial plan is on the left, I plan to have 3 text input boxes, a large calculate button and an output box. The window will not be too big and I will fix the width and height, so … Read more

The first refinement i wish to make is to make the inputs for Day and Month to be ComboBoxes. In order to do this I first need to create two arrays containing all the values for the days(0 – 31) and months(“—” to “December”). The arrays will both store these values as strings and then … Read more