C#公历日期转农历日期

    class LunisolarCalendaUtil
    {
        ///<summary>
        /// 十天干
        ///</summary>
        private static string[] tg = { "甲", "乙", "丙", "丁", "戊", "己", "庚", "辛", "壬", "癸" };

        ///<summary>
        /// 十二地支
        ///</summary>
        private static string[] dz = { "子", "丑", "寅", "卯", "辰", "巳", "午", "未", "申", "酉", "戌", "亥" };

        ///<summary>
        /// 十二生肖
        ///</summary>
        private static string[] sx = { "鼠", "牛", "虎", "免", "龙", "蛇", "马", "羊", "猴", "鸡", "狗", "猪" };

        ///<summary>
        /// 农历月
        ///</summary>

        ///<return s></return s>
        private static string[] months = { "正", "二", "三", "四", "五", "六", "七", "八", "九", "十", "十一", "十二(腊)" };

        ///<summary>
        /// 农历日
        ///</summary>
        private static string[] days1 = { "初", "十", "廿", "三" };
        ///<summary>
        /// 农历日
        ///</summary>
        private static string[] days = { "一", "二", "三", "四", "五", "六", "七", "八", "九", "十" };


        ///<summary>
        /// 返回农历天干地支年
        ///</summary>
        ///<param name="year">农历年</param>
        ///<return s></return s>
        private static string GetLunisolarYear(int year)
        {
            if (year > 3)
            {
                int tgIndex = (year - 4) % 10;
                int dzIndex = (year - 4) % 12;

                return string.Concat(tg[tgIndex], dz[dzIndex], "[", sx[dzIndex], "]");
            }

            throw new ArgumentOutOfRangeException("无效的年份!");
        }


        ///<summary>
        /// 返回农历月
        ///</summary>
        ///<param name="month">农历月份</param>
        ///<return s></return s>
        private static string GetLunisolarMonth(int month)
        {
            if (month < 13 && month > 0)
            {
                return months[month - 1];
            }

            throw new ArgumentOutOfRangeException("无效的月份!");
        }

        ///<summary>
        /// 返回农历日
        ///</summary>
        ///<param name="day">农历天</param>
        ///<return s></return s>
        private  static string GetLunisolarDay(int day)
        {
            if (day > 0 && day < 32)
            {
                if (day != 20 && day != 30)
                {
                    return string.Concat(days1[(day - 1) / 10], days[(day - 1) % 10]);
                }
                else
                {
                    return string.Concat(days[(day - 1) / 10], days1[1]);
                }
            }

            throw new ArgumentOutOfRangeException("无效的日!");
        }


        /// <summary>
        /// 返回农历年月日表示
        /// </summary>
        /// <param name="dateTime">公历日期</param>
        /// <returns></returns>
        public static string GetLunisolarCalenda(DateTime dateTime)
        {
            bool isleap = false;

            Calendar calendar = new ChineseLunisolarCalendar();
            int year = calendar.GetYear(dateTime);
            int month = calendar.GetMonth(dateTime);
            int day = calendar.GetDayOfMonth(dateTime);

            //获取闰月，0 则表示没有闰月.当之前的月份都闰月存在,则需要当前月份减1
            int leapMonth = calendar.GetLeapMonth(year);
            if (leapMonth > 0)
            {
                if (leapMonth <= month)
                {
                    if (leapMonth == month)
                    {
                        //农历闰月
                        isleap = true;
                    }

                    //月份修正
                    month--;
                }
            }
            return string.Concat(GetLunisolarYear(year), "年", isleap ? "闰" : string.Empty, GetLunisolarMonth(month), "月", GetLunisolarDay(day));
        }
    }

　　

实现效果如下：

        static void Main(string[] args)
        {
            //公历转农历
            DateTime dateTime = new DateTime(2020, 5, 23);  //公历日期
            Console.WriteLine($"公历{dateTime.ToShortDateString()}-->{ LunisolarCalendaUtil.GetLunisolarCalenda(dateTime)}");

            Console.ReadKey();
        }

引用内容：https://www.cnblogs.com/jackcheblog/p/7209947.html