判断两个时间间隔是否是自然月

 /// <summary>
        ///  判断两个时间间隔是否是自然月
        /// </summary>
        /// <param name="date1"></param>
        /// <param name="date2"></param>
        /// <returns></returns>
        public static bool isNaturalMonth(DateTime date1, DateTime date2)
        {
            int startYear = date1.Year;
            int startMonth = date1.Month;
            int startDay = date1.Day;
            int endYear = date2.Year;
            int endMonth = date2.Month;
            int endDay = date2.Day;

            if (startYear != endYear)
            {
                return false;
            }
            if (startMonth != endMonth)
            {
                return false;
            }

            if (startDay == 1)
            {
                if (endMonth == 2)
                {
                    if (endYear % 4 == 0 && endYear % 100 != 0 || endYear % 400 == 0)
                    {
                        if (endDay == 29)
                            return true;
                    }
                    else
                    {
                        if (endDay == 28)
                            return true;
                    }
                }
                else
                {
                    if (endMonth == 1 || endMonth == 3 || endMonth == 5 || endMonth == 7 || endMonth == 8 || endMonth == 10 || endMonth == 12)
                    {
                        if (endDay == 31)
                            return true;
                    }
                    else
                    {
                        if (endDay == 30)
                            return true;
                    }
                }
            }
            return false;


        }