using System;

public class Program

{

    public static void Main()

    {

        var tmpb = new DateTime(2016, 12, 1);

        var tmpe = new DateTime(2030, 12, 31);

        var partTimeGrade = 0.5d;

        var daysTotal = (tmpe - tmpb).Days + 1;     

        var countLinear = 0d;

        var countLeap = 0d;

        var days = 0;

        var dueDate = new DateTime(2018, 12, 1);

        var dueDate2 = new DateTime(2020, 12, 1);

        var dueDate3 = new DateTime(2022, 12, 1);

        var dueDate4 = new DateTime(2024, 12, 1);

        var dueDate5 = new DateTime(2026, 12, 1);

        var leapDays = 0;

        while (days < daysTotal) {

            var tmpDate = tmpb.AddDays(days);

            countLinear += 1d / 365 * partTimeGrade;

            countLeap += 1d / (DateTime.IsLeapYear(tmpDate.Year) ? 366 : 365) * partTimeGrade;

            var isLeapYearFirst = DateTime.IsLeapYear(tmpb.Year);

            var isLeapYearLast = DateTime.IsLeapYear(tmpDate.Year);

            var daysUntilMarch = DateTime.IsLeapYear(tmpb.Year) ? 29 : 28;

            var daysToFeb29 = Math.Max(0, (new DateTime(Math.Min(new DateTime(tmpb.Year, 2, daysUntilMarch).Ticks, tmpe.Ticks)) - new DateTime(Math.Max(new DateTime(tmpb.Year, 2, 1).Ticks, tmpb.Ticks))).Days + 1);

            double additionalDay = 0;

            if (isLeapYearFirst) {

                // erstes jahr: ist EIN schaltjahr, KEINE tage im februar

                // letztes jahr: ist KEIN schaltjahr

                if (daysToFeb29 == 0 && !isLeapYearLast) { //  && Math.Truncate(tmpFactor) - tmpFactor < 0

                    // additionalDay = 1;

                }

​

            } else { 

                // erstes jahr: ist KEIN schaltjahr, HAT tage im februar

                // letztes jahr: ist EIN schaltjahr

                if (daysToFeb29 != 0 && isLeapYearLast) { //  && Math.Truncate(tmpFactor) - tmpFactor < 0

                    additionalDay = 1;

                }

            }

            if (tmpDate.Ticks == dueDate.Ticks || tmpDate.Ticks == dueDate2.Ticks || tmpDate.Ticks == dueDate3.Ticks || tmpDate.Ticks == dueDate4.Ticks ) { // || tmpDate.Ticks == dueDate5.Ticks

                // Console.WriteLine("Counter at dueDate:" + countLinear + " " + countLeap);

                Console.WriteLine("Hit! " + days + "/" + (days + additionalDay));

                Console.WriteLine("Leapdays " + leapDays);

                Console.WriteLine("additionalDay " +  additionalDay);

                Console.WriteLine(" ");

            }

            days++;

        }

        var guessed = 365 / partTimeGrade;

        Console.WriteLine(Math.Ceiling(guessed));

        // shifting condition didn't match so we'll add the leap day

        leapDays++;

        var guessed2 = 365 / partTimeGrade * 2 + leapDays;

        Console.WriteLine(Math.Ceiling(guessed2));

        // schaltjahr schon gezählt

        // leapDays++;

        var guessed3 = 365 / partTimeGrade * 3 + leapDays;

        Console.WriteLine(Math.Ceiling(guessed3));

        // shifting condition didn't match so we'll add the leap day

        leapDays++;

        var guessed4 = 365 / partTimeGrade * 4 + leapDays;

        Console.WriteLine(Math.Ceiling(guessed4));

/*      

        // schaltjahr schon gezählt

        leapDays++;

        var guessed5 = 365 / partTimeGrade * 5 + leapDays;

        Console.WriteLine(Math.Ceiling(guessed5));

        //

        */

    }

}