using System;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        string json = @"{

                'Header': {

                    'UserID': 'xxxxxx',

                    'MessageID': 'xxxxxx',

                    'CorrelationID': 'xxxx',

                    'DateTime': '2018-02-12T15:31:18+00:00',

                    'ReqID': 'xxx'

                },

                'ResultSet': {

                    'Tier': {

                        'CardSuffix': '91',

                        'RetentionDeadline': '2022-02-27T16:00:00+00:00',

                        'PointsRequireToQualify': 'xxxxx',

                        'QualifyingDeadline': '2022-02-27T16:00:00+00:00',

                        'SignupDate': '2020-08-07',

                        'IssuedDate': '2021-06-15',

                        'JoiningDateTime': '2010-03-31T10:10:00+00:00',

                        'RequireToUpgradeInYear': '288886',

                        'YearlyUpgradeDeadline': '2022-02-27T16:00:00+00:00',

                        'CurrentCardDesc': 'xxxxxxxx',

                        'NextCardDesc': 'xxxxxxxxx',

                        'CurrentTierPoints': '0',

                        'UpdatedDateTime': '2023-01-09T17:43:54.844+00:00',

                        'LastRefreshedDateTime': '2022-02-10T07:45:13+00:00'

                    }

                }

            }";

        JObject obj = JObject.Parse(json);

        //Console.WriteLine(JsonConvert.DeserializeObject(json, new JsonSerializerSettings(){DateTimeZoneHandling = DateTimeZoneHandling.Utc}));

        obj["ResultSet"]["Tier"]["RetentionDeadline"] = TimeZoneInfo.ConvertTimeBySystemTimeZoneId(new DateTimeOffset(Convert.ToDateTime(obj["ResultSet"]["Tier"]["RetentionDeadline"])), "Singapore Standard Time").ToString("yyyy-MM-ddTH:mm::sszzz");

        //second field....

        //third field....

        //Dont' want to add each field here! Need to convert or deserialize every dateTime property to SGT time with offset on the single settings

        Console.WriteLine(obj);

    }

}