Calculate the daycode of a date

Long time ago, by means of Bussiness Basic, I had this problem as "homework". It did was a headache and there was no Wikipedia nor Internet, just some colleagues comments that really did their best. Allow me to contribute with the following code:

        static void Main(string[] args)
        {
           System.Globalization.CultureInfo ci = 
               new System.Globalization.CultureInfo("en-US");
           System.Globalization.CultureInfo.DefaultThreadCurrentCulture = 
               ci;
           Int32 initYear = 1990;
           Int32 curYear = initYear;
           DateTime dt = new DateTime(curYear, 1, 1);
           DateTime dtStop = DateTime.Today;
           Int32 nErr1, nErr2, nDates;
            Int32 code0, code1, code2;
            do
            {
                Console.Write(dt.ToString("yyyy/MM/dd"));
                code0 = (Int32)dt.DayOfWeek;
                code1 = dateDaycode(dt.Year, dt.Month, dt.Day);
                if (code0 != code1)
                    nErr1++;
                code2 = dateDaycodeWiki(dt.Year, dt.Month, dt.Day);
                if (code0 != code2)
                    nErr2++;
                Console.WriteLine();
                dt = dt.AddDays(1);
                if (dt.Year != curYear)
                {
                    curYear++;
                    dt = new DateTime(curYear, 1, 1);
                }
                nDates++;
            } while (dt <= dtStop);
            if (nErr1 != 0)
                Console.WriteLine(nErr1.ToString() + " code 1 errors found ");
            if (nErr2 != 0)
                Console.WriteLine(nErr2.ToString() + " code 2 errors found ");
                   Console.WriteLine(nDates.ToString() + " total days between dates 01/01/" + 
                   initYear.ToString() + " and " + dtStop.ToShortDateString());
           Console.WriteLine("Press Enter to exit");
           Console.ReadLine();

        }
        public int dateDaycode(int year, int month, int day)
        {
            //Using Zeller's formula
            int d1, d2, d3, d4, code;
            if (month == 1)
            {
                month = 13; year--;
            }
            if (month == 2)
            {
                month = 14; year--;
            }
            d1 = year / 4;
            d2 = year / 100;
            d3 = year / 400;
            d4 = day + 2 * month + 3 * (month + 1) / 5 + year;
            code = (d4 + d1 - d2 + d3 + 1) % 7;
            return code;
            // code will be sun=0,mon=1,tue=2,wen=3,thu=4,fri=5,sat=6
        }
        public int dateDaycodeWiki(int year, int month, int day)
        {
        /* see http://es.wikipedia.org/wiki/Congruencia_de_Zeller
         or http://en.wikipedia.org/wiki/Zeller%27s_congruence */

            Single h;
            Int32 code;
            if (month == 1)
            {
                month = 13; year--;
            }
            if (month == 2)
            {
                month = 14; year--;
            }
            h = (day + (month + 1) * 13 / 5 + year + year / 4 + 6 * (year / 100) + year / 400) % 7;
            // h: 0=sat, 1=sun, 2=mon, ...., 6=friday
            code = (int) (Math.Floor(h) + 6) % 7;
            // code will be sun=0,mon=1,tue=2,wen=3,thu=4,fri=5,sat=6
        }