using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var dateTimes = GetDateTimes();

        foreach (var dateTime in dateTimes)

        {

            if (dateTime is null)

                continue;

            Console.WriteLine(dateTime.Year.ToString() + " " + dateTime.Month.ToString());

        }

    }

    public static IEnumerable<DateTime?> GetDateTimes()

    {

        return new List<DateTime?> { new DateTime(2021, 03, 22), null, DateTime.Now };

    }

}