using System;

using System.Collections.ObjectModel;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var timezones = GetTimeZoneInThisHour(12);

        foreach(var tt in timezones){

            Console.WriteLine(tt);  

        }       

    }

    public static List<string> GetTimeZoneInThisHour(int hourOfDay){

        ReadOnlyCollection<TimeZoneInfo> tz = TimeZoneInfo.GetSystemTimeZones();

        List<string> timezones = new List<string>();

        foreach(var t in tz){

            var dt = TimeZoneInfo.ConvertTimeFromUtc(System.DateTime.UtcNow, t);

            if(dt.Hour == hourOfDay)

                timezones.Add(t.Id.ToString());

        }

        return timezones;

    }

}