Trading hours parsing

TradingHours.cs

 using TimeZoneConverter; // https://www.nuget.org/packages/TimeZoneConverter/
        
        public void contractDetails(int reqId, ContractDetails contractDetails)
        {
            // Parse trading hours
            List<DateRange> tradingHours = new List<DateRange>();
            if (contractDetails.LiquidHours != null)
                foreach (string dateStr in contractDetails.LiquidHours.Split(new char[] { ';' }, StringSplitOptions.RemoveEmptyEntries))
                {
                    // Skip if it is closed this date
                    if (dateStr.Substring(9) == "CLOSED")
                        continue;

                    // Check length
                    if (dateStr.Length != 18)
                        throw new Exception("Unknown liquid hours datetime format.");

                    // Parse, example: 20170515:0930-1600
                    int year = int.Parse(dateStr.Substring(0, 4));
                    int month = int.Parse(dateStr.Substring(4, 2));
                    int day = int.Parse(dateStr.Substring(6, 2));
                    int hourFrom = int.Parse(dateStr.Substring(9, 2));
                    int minutesFrom = int.Parse(dateStr.Substring(11, 2));
                    int hourTo = int.Parse(dateStr.Substring(14, 2));
                    int minutesTo = int.Parse(dateStr.Substring(16, 2));

                    // Is it today?
                    DateTime from = new DateTime(year, month, day, hourFrom, minutesFrom, 0);
                    DateTime to = new DateTime(year, month, day, hourTo, minutesTo, 0);

                    // Convert to UTC
                    TimeZoneInfo sourceTimeZone = TimeZoneInfo.FindSystemTimeZoneById(TZConvert.IanaToWindows(contractDetails.TimeZoneId));
                    from = TimeZoneInfo.ConvertTimeToUtc(from, sourceTimeZone);
                    to = TimeZoneInfo.ConvertTimeToUtc(to, sourceTimeZone);

                    // Save
                    tradingHours.Add(new DateRange()
                    {
                        From = from,
                        To = to
                    });
                }
        }