using System;

public class Program

{

    public static void Main()

    {

        string tdate = "20221021";

​

            int year = tdate.Substring(0, 4).TryParseDate( DateTime.MaxValue.Year);

            int month = tdate.Substring(4, 2).TryParseDate(12);

            int day = tdate.Substring(6, 2).TryParseDate(31); 

        Console.WriteLine($"{year}-{month}-{day}");

    }

}

​

 /// <summary>

    /// Class IntParsers.

    /// </summary>

    public static class IntParsers

    {

        /// <summary>

        /// Tries the parse date.

        /// </summary>

        /// <param name="value">The value.</param>

        /// <param name="maxValue">The maximum value.</param>

        /// <returns>System.Int32.</returns>

        public static int TryParseDate(this string value, int maxValue) 

        {

            int ret = int.Parse(value);

            ret = ret < 1 ? 1 : ret;

            ret = ret > maxValue ? maxValue : ret;

            return ret;

        }

​

        /// <summary>

        /// Tries the parse to date.

        /// </summary>

        /// <param name="year">The year.</param>

        /// <param name="month">The month.</param>

        /// <param name="day">The day.</param>

        /// <returns>DateTime.</returns>

        /// <remarks>

        /// The exceptions should never be hit under normal conditions. 

        /// The junk style fix was to pass QA only.

        /// </remarks>

        public static DateTime TryParseToDate(int year, int month, int day) 

        {

            try

            {

                return new DateTime(year, month, day);

            }

            catch

            {

                try

                {

                    return new DateTime(year, month, 30);

                }

                catch

                {

                    try

                    {

                        return new DateTime(year, month, 29);

                    }

                    catch

                    {

                        return new DateTime(year, month, 28);

                    }

                }

            }

        }

    }