C#-Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace der13
{
    class Program
    {
        static int[] weekDayCounter = new int[7];
        static int counter;
        static string weekdayMax;
        static string weekdayMin;
        static int day;
        static int daysave;
        static float i = 1;
        static float numbersave;
        static bool switchYear;

         static void Main(string[] args)
              {
                  Render();
            Console.WriteLine(Convert.ToString(weekDayCounter.Max()));
            if (weekDayCounter.ToList().IndexOf(weekDayCounter.Max()) == 0) { weekdayMax = "Monday"; }
            else if (weekDayCounter.ToList().IndexOf(weekDayCounter.Max()) == 1) { weekdayMax = "Tuesday"; }
            else if (weekDayCounter.ToList().IndexOf(weekDayCounter.Max()) == 2) { weekdayMax = "Wednesday"; }
            else if (weekDayCounter.ToList().IndexOf(weekDayCounter.Max()) == 3) { weekdayMax = "Thursday"; }
            else if (weekDayCounter.ToList().IndexOf(weekDayCounter.Max()) == 4) { weekdayMax = "Friday"; }
            else if (weekDayCounter.ToList().IndexOf(weekDayCounter.Max()) == 5) { weekdayMax = "Saturday 	"; }
            else if (weekDayCounter.ToList().IndexOf(weekDayCounter.Max()) == 6) { weekdayMax = "Sunday 	"; }
            Console.WriteLine("The day with the most 13th. is the {0}.", weekdayMax);
            if (weekDayCounter.ToList().IndexOf(weekDayCounter.Min()) == 0) { weekdayMin = "Monday"; }
            else if (weekDayCounter.ToList().IndexOf(weekDayCounter.Min()) == 1) { weekdayMin = "Tuesday"; }
            else if (weekDayCounter.ToList().IndexOf(weekDayCounter.Min()) == 2) { weekdayMin = "Wednesday"; }
            else if (weekDayCounter.ToList().IndexOf(weekDayCounter.Min()) == 3) { weekdayMin = "Thursday"; }
            else if (weekDayCounter.ToList().IndexOf(weekDayCounter.Min()) == 4) { weekdayMin = "Friday"; }
            else if (weekDayCounter.ToList().IndexOf(weekDayCounter.Min()) == 5) { weekdayMin = "Saturday 	"; }
            else if (weekDayCounter.ToList().IndexOf(weekDayCounter.Min()) == 6) { weekdayMin = "Sunday 	"; }
            Console.WriteLine("The day with the less 13th. is the {0}.", weekdayMin);
            Console.ReadKey();

        }

         private static void Render()
         {
             for (i = 1; i <= 2018; i++)
             {
                 Schaltjahr();
                 if (i <= 2018 & switchYear == true)
                 {
                     Tag31();
                     Tag29();
                     Tag31();
                     Tag30();
                     Tag31();
                     Tag30();
                     Tag31();
                     Tag31();
                     Tag30();
                     Tag31();
                     Tag30();
                     Tag31();
                 }
                 if (i <= 2018 & switchYear == false)
                 {
                     Tag31();
                     Tag28();
                     Tag31();
                     Tag30();
                     Tag31();
                     Tag30();
                     Tag31();
                     Tag31();
                     Tag30();
                     Tag31();
                     Tag30();
                     Tag31();
                 }
             }
         }

         private static void Schaltjahr()
         {
             switchYear = true;
             numbersave = i / 100;
             if (numbersave == (int)numbersave)
             {
                 switchYear = false;
             }

                 numbersave = i / 400;
                 if (numbersave == (int)numbersave)
                 {
                     switchYear = true;
                     numbersave = i / 4;
                     if (numbersave != (int)numbersave & switchYear != false)
                     {
                         switchYear = false;
                     }
                     else
                     {
                         switchYear = true;
                     }
                 }
             
         }
         private static void Tag28()
         {
             while (day <= 7) 
             {
                 Provider();
                 if (counter == 28) { counter = 0; break; }
             }
         }

         private static void Tag29()
         {
             while (day <= 7)
             {
                 Provider();
                 if (counter == 29) { counter = 0; break; }
             }
         }

         private static void Tag31()
         {
             while(day <= 7) 
             {
                 Provider();
                 if (counter == 31) { counter = 0; break; }
             }
         }
         private static void Tag30()
         {
             while (day <= 7) 
             {
                 Provider();
                 if (counter == 30) { counter = 0; break; }
             }
         }

         private static void Tagsaver()
         {
             if (daysave == 1) { weekDayCounter[0]++; }
             if (daysave == 2) { weekDayCounter[1]++; }
             if (daysave == 3) { weekDayCounter[2]++; }
             if (daysave == 4) { weekDayCounter[3]++; }
             if (daysave == 5) { weekDayCounter[4]++; }
             if (daysave == 6) { weekDayCounter[5]++; }
             if (daysave == 7) { weekDayCounter[6]++; }

         }

         private static void Provider()
         {
             counter++;
             day++;
             if (counter == 13) { daysave = day; Tagsaver(); }
             if (day == 7) { day = 0; }
         }
      
    }
}