TimeZoneConverter.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Xml;

namespace tztest
{
    class Program
    {
        private static XmlDocument LoadCldrXml(string path)
        {
            var xmlDoc = new XmlDocument();
            xmlDoc.Load($"/home/username/Desktop/tztest/cldr" + path);
            return xmlDoc;
        }

        private static Dictionary<string, string> WinToIANA(
            Dictionary<string, TimeZoneInfo> zoneById,
            Dictionary<string, string[]> zoneToAlias)
        {
            var xmlDoc = LoadCldrXml("/supplemental/windowsZones.xml");
            var zoneList = xmlDoc.SelectNodes("//supplementalData/windowsZones/mapTimezones/mapZone");
            var winToIana = new Dictionary<string, string>();
            foreach (XmlNode node in zoneList)
            {
                var winId = node.Attributes["other"].Value;
                var ianaId = node.Attributes["type"].Value;
                if (!winToIana.TryGetValue(winId, out var prevIanaName) || prevIanaName.StartsWith("Etc/"))
                {
                    if (!zoneById.ContainsKey(ianaId))
                    {
                        ianaId = zoneToAlias[ianaId].FirstOrDefault(_ => zoneById.ContainsKey(_)) ?? ianaId;
                    }
                    winToIana[winId] = ianaId;
                }
            }
            winToIana["UTC"] = "UTC";
            return winToIana;
        }

        private static Dictionary<string, string> ReadZoneNames(string culture)
        {
            var xmlDoc = LoadCldrXml($"/main/{culture}.xml");
            var zoneToName = new Dictionary<string, string>();
            var itemNodes = xmlDoc.SelectNodes("//ldml/dates/timeZoneNames/zone/exemplarCity");
            foreach (XmlNode item in itemNodes)
            {
                var zoneId = item.ParentNode.Attributes["type"].Value;
                var zoneName = item.InnerText;
                zoneToName[zoneId] = zoneName;
            }
            var utcNode = xmlDoc.SelectSingleNode("//ldml/dates/timeZoneNames/zone[@type='Etc/UTC']/long/standard");
            zoneToName["UTC"] = utcNode.InnerText;
            zoneToName["Etc/GMT+12"] = "Линия перемены дат"; // International Date Line, Линия перемены дат, Die Datumsgrenze
            return zoneToName;
        }

        private static Dictionary<string, string[]> ReadZoneAliases()
        {
            var xmlDoc = LoadCldrXml("/bcp47/timezone.xml");
            var zoneToAlias = new Dictionary<string, string[]>();
            var itemNodes = xmlDoc.SelectNodes("//ldmlBCP47/keyword/key/type");
            foreach (XmlNode item in itemNodes)
            {
                var aliases = item.Attributes["alias"]?.Value?.Split(' ');
                if (aliases != null)
                {
                    foreach (var alias in aliases)
                    {
                        zoneToAlias[alias] = aliases.Where(_ => _ != alias).ToArray();
                    }
                }
            }
            return zoneToAlias;
        }

        static void Main(string[] args)
        {
            var culture = "ru";
            var zoneToName = ReadZoneNames(culture);
            var zoneToAlias = ReadZoneAliases();

            var systemZones = new[] { TimeZoneInfo.FindSystemTimeZoneById("Etc/GMT+12") }
                .Union(TimeZoneInfo.GetSystemTimeZones())
                .ToDictionary(_ => _.Id);

            foreach (var z in systemZones.Values)
            {
                if (!zoneToName.TryGetValue(z.Id, out var name))
                {
                    if (zoneToAlias.TryGetValue(z.Id, out var aliases))
                    {
                        foreach (var aliasId in aliases)
                        {
                            if (zoneToName.TryGetValue(aliasId, out name))
                            {
                                break;
                            }
                        }
                    }
                    if (name == null)
                    {
                        name = z.Id.Split('/').Last().Replace('_', ' ');
                    }
                }

                if (z.Id == "UTC")
                {
                    Console.WriteLine($"(UTC) {name}");
                }
                else
                {
                    var sign = '-';
                    var offset = z.BaseUtcOffset;
                    if (offset >= TimeSpan.Zero)
                    {
                        sign = '+';
                    }
                    else
                    {
                        offset = -offset;
                    }
                    var hours = offset.Hours.ToString("00");
                    var minutes = offset.Minutes.ToString("00");

                    Console.WriteLine($"{z.Id} - (UTC{sign}{hours}:{minutes}) {name}");
                }
            }

            Console.WriteLine("================================");
            var winToIana = WinToIANA(systemZones, zoneToAlias);
            foreach (var z in winToIana.Values.Where(_ => !systemZones.ContainsKey(_)))
            {
                Console.WriteLine(z);
            }

            foreach (var pair in winToIana)
            {
                Console.WriteLine($"WHEN '{pair.Key}' THEN '{pair.Value}'");
            }

        }
    }
}