A Date format converter that converts date and time consistently irrespective of the hosting platform or daylight savings

UtcSydneyDateFormatConverter.cs

using System;
using System.Globalization;
using Newtonsoft.Json;
using Newtonsoft.Json.Converters;

public class UtcSydneyDateFormatConverter : IsoDateTimeConverter
    {
        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            DateTimeStyles = DateTimeStyles.AdjustToUniversal;
            base.WriteJson(writer, value, serializer);
        }

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue,
            JsonSerializer serializer)
        {
            var utcDateTime = DateTime.Parse(reader.Value.ToString());
            var tz = CreateAestTimeZone();
            return (DateTimeOffset) TimeZoneInfo.ConvertTimeFromUtc(utcDateTime, tz);
        }

        private TimeZoneInfo CreateAestTimeZone()
        {
            // Define transition times to/from DST
            TimeZoneInfo.TransitionTime startTransition, endTransition;
            startTransition = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(new DateTime(1, 1, 1, 2, 0, 0),
                4, 1, DayOfWeek.Sunday);
            endTransition = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(new DateTime(1, 1, 1, 2, 0, 0),
                10, 1, DayOfWeek.Sunday);
            // Define adjustment rule
            TimeSpan delta = new TimeSpan(1, 0, 0);
            TimeZoneInfo.AdjustmentRule adjustment;
            adjustment = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(new DateTime(1999, 10, 1),
                DateTime.MaxValue.Date, delta, startTransition, endTransition);
            // Create array for adjustment rules
            TimeZoneInfo.AdjustmentRule[] adjustments = {adjustment};
            // Define other custom time zone arguments
            string displayName = "(GMT+10:00) Australia/Sydney";
            string standardName = "Australian Eastern Standard Time";
            string daylightName = "Australian Eastern Daylight Time";
            TimeSpan offset = new TimeSpan(11, 0, 0);
            TimeZoneInfo aest = TimeZoneInfo.CreateCustomTimeZone(standardName, offset, displayName, standardName,
                daylightName, adjustments);
            return aest;
        }
    }

UtcSydneyDateFormatConverter_NoDst.cs

public class UtcSydneyDateFormatConverter : IsoDateTimeConverter
    {
        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            DateTimeStyles = DateTimeStyles.AdjustToUniversal;
            base.WriteJson(writer, value, serializer);
        }

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue,
            JsonSerializer serializer)
        {
            var utcDateTime = DateTime.Parse(reader.Value.ToString());
            var tz = CreateAestTimeZone();
            return (DateTimeOffset) TimeZoneInfo.ConvertTimeFromUtc(utcDateTime, tz);
        }

        private TimeZoneInfo CreateAestTimeZone()
        {
            string displayName = "(GMT+10:00) Australia/Sydney";
            string standardName = "Australian Eastern Standard Time";
            string daylightName = "Australian Eastern Daylight Time";
            TimeSpan offset = new TimeSpan(11, 0, 0);
            TimeZoneInfo aest = TimeZoneInfo.CreateCustomTimeZone(standardName, offset, displayName, standardName);
            return aest;
        }
    }