Started work on a calculator 'lib' that the app is going to use

lib/DayCalculator.dart

@@ -0,0 +1,10 @@
+// Based on this article:
+// https://artofmemory.com/blog/how-to-calculate-the-day-of-the-week-4203.html
+
+class DayCalculator {
+  // Calculates (YY + floor(YY / 4)) % 7
+  static int getYearValue(int year){
+    var yy = year % 100;
+    return (yy + (yy / 4).floor()) % 7;
+  }
+}