using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var timeZoneInfo = TimeZoneInfo.GetSystemTimeZones().FirstOrDefault(tzi => tzi.Id.Equals("Europe/London", StringComparison.InvariantCultureIgnoreCase));

​

        Console.WriteLine($"No. of adjustment rules: {timeZoneInfo.GetAdjustmentRules().Count()}");

        var firstRule = timeZoneInfo.GetAdjustmentRules().FirstOrDefault(r => new DateTime(2021,03,28,1,59,0) >= r.DateStart && new DateTime(2021,03,28,1,59,0) <= r.DateEnd);

        Console.WriteLine($"            Day: {firstRule.DaylightTransitionStart.Day}");

        Console.WriteLine($"      DayOfWeek: {firstRule.DaylightTransitionStart.DayOfWeek}");

        Console.WriteLine($"IsFixedDateRule: {firstRule.DaylightTransitionStart.IsFixedDateRule}");

        Console.WriteLine($"          Month: {firstRule.DaylightTransitionStart.Month}");

        Console.WriteLine($"      TimeOfDay: {firstRule.DaylightTransitionStart.TimeOfDay}");

        Console.WriteLine($"           Week: {firstRule.DaylightTransitionStart.Week}");

        Console.WriteLine($"Offset at 01:59 on 2021-03-28: {timeZoneInfo.GetUtcOffset(new DateTime(2021,03,28,1,59,0)).Hours}");

​

        Console.WriteLine($"Offset at 02:00 on 2021-03-28: {timeZoneInfo.GetUtcOffset(new DateTime(2021,03,28,2,0,0)).Hours}");

    }

}