Fix TimeZoneNotFoundException

[fernandolguevara]

Fix #17 throws TimeZoneNotFoundException when call GetTimeZoneInfo("UTC")

[mattjohnsonpint]

Thanks, but it's odd this needs special handling. "UTC" is valid for both IANA and Windows. Is there something special about why this doesn't work as is on Mac?

[fernandolguevara]

@mj1856

below is the source code of TimeZoneInfo for operative systems based on unix, so, there is a special consideration for "UTC" id

   public static TimeZoneInfo FindSystemTimeZoneById(string id)
        {
            // Special case for Utc as it will not exist in the dictionary with the rest
            // of the system time zones.  There is no need to do this check for Local.Id
            // since Local is a real time zone that exists in the dictionary cache
            if (string.Equals(id, UtcId, StringComparison.OrdinalIgnoreCase))
            {
                return Utc;
            }
           .....

[fernandolguevara]

@mj1856 another possible solution could be adding TimeZoneInfo.Utc to the SystemTimeZones dictionary

[mattjohnsonpint]

Makes sense. Thanks!