Get Australian timezone name by state using Noda Time

In this post I will show how to convert UTC date to local Australian date by state. The result will be in the format of {localDateTime} – {timezone name} ({timezone abbreviation}) e.g “14/10/2018 20:30 – Australian Eastern Standard Time (AEST)”

I added this method as an extension on DateTime

    public static class DateTimeExtensions
    {
        private static IDictionary<string, DateTimeZone> dateTimeZones = new Dictionary<string, DateTimeZone>
        {
            { "NSW", DateTimeZoneProviders.Tzdb["Australia/Sydney"] },
            { "VIC", DateTimeZoneProviders.Tzdb["Australia/Melbourne"] },
            { "SA", DateTimeZoneProviders.Tzdb["Australia/Adelaide"] },
            { "QLD", DateTimeZoneProviders.Tzdb["Australia/Brisbane"] },
            { "NT", DateTimeZoneProviders.Tzdb["Australia/Darwin"] },
            { "TAS", DateTimeZoneProviders.Tzdb["Australia/Hobart"] },
            { "WA", DateTimeZoneProviders.Tzdb["Australia/Perth"] },
            { "ACT", DateTimeZoneProviders.Tzdb["Australia/Sydney"] }
        };

        private static readonly IDictionary<(string state, bool isDaylightSaving), string> timezoneNames = new Dictionary<(string state, bool isDaylightSaving), string>
        {
            { (state: "NSW", isDaylightSaving: false), "Australian Eastern Standard Time (AEST)" },
            { (state: "VIC", isDaylightSaving: false), "Australian Eastern Standard Time (AEST)" },
            { (state: "WA", isDaylightSaving: false), "Australian Western Standard Time (AWST)" },
            { (state: "SA", isDaylightSaving: false), "Australian Central Standard Time (ACST)" },
            { (state: "TAS", isDaylightSaving: false), "Australian Eastern Standard Time (AEST)" },
            { (state: "QLD", isDaylightSaving: false), "Australian Eastern Standard Time (AEST)" },
            { (state: "ACT", isDaylightSaving: false), "Australian Eastern Standard Time (AEST)" },
            { (state: "NT", isDaylightSaving: false), "Australian Central Standard Time (ACST)" },
            { (state: "NSW", isDaylightSaving: true), "Australian Eastern Daylight Time (AEDT)" },
            { (state: "VIC", isDaylightSaving: true), "Australian Eastern Daylight Time (AEDT)" },
            { (state: "WA", isDaylightSaving: true), "Australian Western Standard Time (AWST)" },
            { (state: "SA", isDaylightSaving: true), "Australian Central Daylight Time (ACDT)" },
            { (state: "TAS", isDaylightSaving: true), "Australian Eastern Daylight Time (AEDT)" },
            { (state: "QLD", isDaylightSaving: true), "Australian Eastern Standard Time (AEST)" },
            { (state: "ACT", isDaylightSaving: true), "Australian Eastern Daylight Time (AEDT)" },
            { (state: "NT", isDaylightSaving: true), "Australian Central Standard Time (ACST)" }
        };

        private static ZonedDateTime ConvertUtcToZonedDateTime(this DateTime dateTime, string state)
        {
            if (!dateTimeZones.ContainsKey(state))
            {
                throw new NotSupportedException($"State is not supported {state}");
            }

            var time = Instant.FromDateTimeUtc(dateTime.ToUniversalTime());
            var zone = dateTimeZones[state];
            var zonedTime = time.InZone(zone);

            return zonedTime;
        }

        public static DateTimeZonedInfo GetDateTimeZonedInfo(this DateTime dateTime, string state)
        {
            var utcDate = dateTime.ToUniversalTime();
            var zonedDateTime = utcDate.ConvertUtcToZonedDateTime(state);
            var timezoneName = timezoneNames[(state, zonedDateTime.IsDaylightSavingTime())];
            
            return new DateTimeZonedInfo
            {
                DateTime = zonedDateTime.ToDateTimeUnspecified(),
                TimezoneName = timezoneName
            };
        }
    }

    public class DateTimeZonedInfo
    {
        public DateTime DateTime { get; set; }
        public string TimezoneName { get; set; }

        public override string ToString()
        {
            return $"{DateTime.ToString("dd/MM/yyyy HH:mm")} - {TimezoneName}";
        }
    }