Japanise new era test program.

ReiwaTestConsole.cs

using System;

namespace ReiwaTestConsole
{
    class Program
    {
        static void Main(string[] args)
        {

            var jc = new System.Globalization.JapaneseCalendar();
            var cultureJp = new System.Globalization.CultureInfo("ja-JP",false);
            cultureJp.DateTimeFormat.Calendar = jc;

            Console.WriteLine("Input-2019/04/30");

            DateTime heisei_dt = new DateTime(2019, 04, 30);

            Console.WriteLine("default culture-yyyy/MM/dd");
            Console.WriteLine(heisei_dt.ToString("yyyy/MM/dd"));

            Console.WriteLine("Japanese Culture - ggyy/MM/dd");
            Console.WriteLine(heisei_dt.ToString("ggyy/MM/dd",cultureJp));

            Console.WriteLine();

            Console.WriteLine("Input-2019/05/01");

            DateTime reiwa_dt = new DateTime(2019, 05, 01);

            Console.WriteLine("default culture-yyyy/MM/dd");
            Console.WriteLine(reiwa_dt.ToString("yyyy/MM/dd"));

            Console.WriteLine("Japanese Culture - ggyy/MM/dd");
            Console.WriteLine(reiwa_dt.ToString("ggyy/MM/dd", cultureJp));

            Console.ReadLine();

        }
    }
}