请问我这个程序是否有内存溢出？

Question

这是一个用C#编写的，用NUnit进行单元测试的程序。要实现对一个日期加一，判断是否合法。请问我这个程序是否有内存溢出？是否还有别的问题？应该如何修改？using System;
using NUnit.Framework;namespace NextDate
{
    class DateType
    {
        public int year;
        public int month;
        public int day;        public DateType(int y, int m, int d)
        {
            year = y;
            month = m;
            day=d;
        }
    }    class NextDate
    {  
        public bool leap(int y)
        {
            if (y % 100 == 0 && y % 400 == 0)
                return true;
            if (y % 100 != 0 && y % 4 == 0)
                return true;
            return false;
        }
        
        public DateType plus(DateType today)
        {
            bool c1,c2;
            DateType tomorrow=new DateType(0,0,0);
            tomorrow.year = today.year;
            tomorrow.month = today.month;
            tomorrow.day = today.day;            c1=(1<=today.day) && (today.day<=31);
            c2 = (1 <= today.month) && (today.month <= 12);
            if(c1==false)
                return new DateType(0,0,0);
            if(c2==false)
                return new DateType(0,0,0);            switch(today.month)
            {
                case 1:
                case 3:
                case 5:
                case 7:
                case 8:
                case 10:
                    if(today.day<31)
                        tomorrow.day=today.day+1;
                    else
                    {
                        tomorrow.day=1;
                        tomorrow.day=today.month+1;
                    }
                    break;
                case 4:
                case 6:
                case 9:
                case 11:
                    if(today.day<30)
                        tomorrow.day = today.day + 1;
                    else
                    {
                        tomorrow.day = 1;
                        tomorrow.day = today.month + 1;
                    }
                    break;
                case 2:
                    if(today.day<28)
                        tomorrow.day = 1;
                    else
                    {
                        if(today.day==28)
                        {
                            if(leap(today.year))
                                tomorrow.day=29;
                            else
                            {
                                tomorrow.day=1;
                                tomorrow.month=3;
                            }
                        }
                        else
                            if(today.day==29)
                            {
                                tomorrow.day=1;
                                tomorrow.month=3;
                            }
                            else
                                return new DateType(0,0,0);
                    }
                    break;
             }             return tomorrow;
        }
    }    [TestFixture]
    class Program
    {
      [Test]
        public static void Main(string[] args)
        {
            NextDate a = new NextDate();            Assert.AreEqual(new DateType(2001, 4, 15), a.plus(new DateType(2001, 4, 15)),"aa");
        }
    }
}