using System;

using System.Text.RegularExpressions;

using System.Globalization;     

public class Program

{

    public static void Main()

    {

        DateTime date;

        DateTime.TryParseExact(

            "Июн 16 2021",

            "MMM d yyyy",

            CultureInfo.CreateSpecificCulture("ru-RU"),

            DateTimeStyles.None,

            out date

        );

​

        Console.WriteLine(date);

    }

}

​