using System;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        var now = DateTime.UtcNow;

        var posix = "EST5EDT,M3.2.0/2,M11.1.0/2";

        var cronSchedule = "*/5 9-17 * * *";

        var cronScheduleDescription = CronExpressionDescriptor.ExpressionDescriptor.GetDescription(cronSchedule, new CronExpressionDescriptor.Options{DayOfWeekStartIndexZero = true, Use24HourTimeFormat = true, Locale = "en"});

        Console.WriteLine(cronScheduleDescription);

        var tz = PosixToTimeZoneInfo(posix);

        var localNow = TimeZoneInfo.ConvertTimeFromUtc(now,tz);

        var wtf = new DateTime(localNow.Year,localNow.Month,localNow.Day,localNow.Hour,localNow.Hour,localNow.Second, DateTimeKind.Local);

        var localNowKind = wtf.Kind;

        var cron = NCrontab.CrontabSchedule.TryParse(cronSchedule, new NCrontab.CrontabSchedule.ParseOptions { IncludingSeconds = false });

        var nextRunLocal=cron.GetNextOccurrence(wtf);

        var nextRunUtc = TimeZoneInfo.ConvertTimeToUtc(nextRunLocal);

        Console.WriteLine($"UTC:     {now}");

        Console.WriteLine($"Local:   {wtf} {localNowKind}");

        Console.WriteLine($"Next:    {nextRunLocal}");

        Console.WriteLine($"NextUTC: {nextRunUtc}");

    }

​

    private static TimeZoneInfo PosixToTimeZoneInfo(string tz)

    {

        var dataParse = Regex.Match(tz, @"((?<TzSet>(?<Id>(?<ST>[a-zA-Z]+)(?<Offset>(-?\d{1,2}(:\d{1,2})?))((?<DT>[a-zA-Z]+))?)(,M)?(?<StartMonth>\d{1,2})?(\.)?(?<StartWeek>\d{1,2})?(\.)?(?<StartDayOfWeek>\d{1,2})?/?(?<StartHour>\d{1,2}(:\d{1,2})?)?(,M)?(?<EndMonth>\d{1,2})?(\.)?(?<EndWeek>\d{1,2})?(\.)?(?<EndDayOfWeek>\d{1,2})?/?(?<EndHour>\d{1,2}(:\d{1,2})?)?))$");

        if (dataParse.Success)

        {

            string Id = dataParse.Groups["Id"].Value;

            TimeZoneInfo timeZoneInfo;

            TimeSpan baseUtcOffset;

            if (dataParse.Groups["Offset"].Value.Contains(":"))

                baseUtcOffset = TimeSpan.Parse(dataParse.Groups["Offset"].Value);

            else

                baseUtcOffset = new TimeSpan(int.Parse(dataParse.Groups["Offset"].Value), 0, 0);

            if (dataParse.Groups["StartMonth"].Value != string.Empty && dataParse.Groups["EndMonth"].Value != string.Empty)

            {

                TimeSpan startTime;

                TimeSpan endTime;

                if (dataParse.Groups["StartHour"].Value == string.Empty)

                {

                    startTime = new TimeSpan(2, 0, 0);

                }

                else

                {

                    if (dataParse.Groups["StartHour"].Value.Contains(":"))

                        startTime = TimeSpan.Parse(dataParse.Groups["StartHour"].Value);

                    else

                    {

                        startTime = new TimeSpan(int.Parse(dataParse.Groups["StartHour"].Value), 0, 0);

                    }

                }

​

                if (dataParse.Groups["EndHour"].Value == string.Empty)

                {

                    endTime = new TimeSpan(2, 0, 0);

                }

                else

                {

                    if (dataParse.Groups["EndHour"].Value.Contains(":"))

                        endTime = TimeSpan.Parse(dataParse.Groups["EndHour"].Value);

                    else

                    {

                        endTime = new TimeSpan(int.Parse(dataParse.Groups["EndHour"].Value), 0, 0);

                    }

                }

​

                TimeZoneInfo.TransitionTime startTransition = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(new DateTime(1, 1, 1, startTime.Hours, startTime.Minutes, 0), int.Parse(dataParse.Groups["StartMonth"].Value), int.Parse(dataParse.Groups["StartWeek"].Value), (DayOfWeek)int.Parse(dataParse.Groups["StartDayOfWeek"].Value));

                TimeZoneInfo.TransitionTime endTransition = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(new DateTime(1, 1, 1, endTime.Hours, endTime.Minutes, 0), int.Parse(dataParse.Groups["EndMonth"].Value), int.Parse(dataParse.Groups["EndWeek"].Value), (DayOfWeek)int.Parse(dataParse.Groups["EndDayOfWeek"].Value));

                TimeZoneInfo.AdjustmentRule adjustmentRule = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(DateTime.MinValue.Date, DateTime.MaxValue.Date, new TimeSpan(1, 0, 0), startTransition, endTransition);

                timeZoneInfo = TimeZoneInfo.CreateCustomTimeZone(Id, -baseUtcOffset, Id, dataParse.Groups["ST"].Value, dataParse.Groups["DT"].Value, new[]{adjustmentRule});

            }

            else

            {

                timeZoneInfo = TimeZoneInfo.CreateCustomTimeZone(Id, -baseUtcOffset, Id, dataParse.Groups["ST"].Value, dataParse.Groups["DT"].Value, null);

            }

            return timeZoneInfo;

        }

        return null;

    }

}