using System;

public class Program

{

    public static void Main()

    {

        var arizonTimeZone = TimeZoneInfo.FindSystemTimeZoneById("US Mountain Standard Time");

        var winterTime = new DateTime(2018, 1, 1, 21, 00,00, System.DateTimeKind.Utc);

        var summerTime = new DateTime(2018, 8, 1, 21, 00,00, System.DateTimeKind.Utc);

        var winterArizonaTimeFromUtc = TimeZoneInfo.ConvertTime(winterTime, arizonTimeZone);

        var summerArizonaTimeFromUtc = TimeZoneInfo.ConvertTime(summerTime, arizonTimeZone);

        Console.WriteLine(winterArizonaTimeFromUtc);

        Console.WriteLine(summerArizonaTimeFromUtc);

    }

}