using System;

using System.Runtime.InteropServices;

public static class Program

{

    public static void Main()

    {

        ExampleMethodUsage();

    }

    public static void ExampleMethodUsage()

    {

        TimeZoneInfo eastTz = GetEasternTimeZoneInfo();

        TimeZoneInfo centralTz = GetCentralTimeZoneInfo();

        TimeZoneInfo pacificTz = GetPacificTimeZoneInfo();

        TimeZoneInfo serverTz = GetServerTimeZoneInfo();

        //Adjust these to check the different conversions between the original times and the final Eastern time strings

        TimeZoneInfo sqlTz = eastTz;

​

        DateTime clientDt = DateTime.Parse("2025-01-01T13:45:58-07:00"); //Client datetime string passed with Pacific timezone will be parsed into server timezone

        DateTime serverDt = DateTime.Now; //DateTime generated by the server is in server timezone

        DateTime sqlDt = DateTime.Parse("01/01/2025 13:45:58"); //DateTime from SQL server in Eastern timezone

        DateOnly sqlDo = DateOnly.Parse("01/01/2025"); //DateOnly from SQL server in Eastern timezone

        TimeOnly sqlTo = TimeOnly.Parse("13:45:58"); //TimeOnly from SQL server in Eastern timezone

​

        //Dates and times originating from the Portal convert from server timezone

        string sClientDt = clientDt.ToEasternTimeZoneString(serverTz);

        string sServerDt = serverDt.ToEasternTimeZoneString(serverTz);

​

        //Dates and times originating from SQL convert from SQL timezone

        string sSqlDt = sqlDt.ToEasternTimeZoneString(sqlTz);

        string sSqlDo = sqlDo.ToEasternTimeZoneString();

        string sSqlTo = sqlTo.ToEasternTimeZoneString(sqlTz);

        Console.WriteLine(sClientDt);

        Console.WriteLine(sServerDt);

        Console.WriteLine(sSqlDt);

        Console.WriteLine(sSqlDo);

        Console.WriteLine(sSqlTo);

    }

​

    public static string ToEasternTimeZoneString(this DateTime dt, TimeZoneInfo sourceTimeZone)

    {

        TimeZoneInfo eastTz = GetEasternTimeZoneInfo();

        return dt.ToTimeZoneString(sourceTimeZone, eastTz);

    }

​

    public static string ToEasternTimeZoneString(this DateOnly dtDo)

    {

        var midnight = new TimeOnly(0, 0, 0);

        DateTime convertedDt = dtDo.ToDateTime(midnight); //No timezone conversion for date-only.  We use the exact date.

        return convertedDt.ToString("MM/dd/yyyy");

    }

    public static string ToEasternTimeZoneString(this TimeOnly dtTo, TimeZoneInfo sourceTimeZone)

    {

        TimeZoneInfo eastTz = GetEasternTimeZoneInfo();

        return dtTo.ToTimeZoneString(sourceTimeZone, eastTz);

    }

    public static string ToTimeZoneString(this DateTime dt, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)

    {

        DateTime convertedDt = dt.ConvertToUnspecifiedDateTimeKind();

        convertedDt = convertedDt.ConvertBetweenTimeZones(sourceTimeZone, destinationTimeZone);

        return convertedDt.ToString("MM/dd/yyyy hh:mm:ss tt");

    }

​

    public static string ToTimeZoneString(this TimeOnly dtTo, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)

    {

        var ts = dtTo.ToTimeSpan();

        var dt = DateTime.Today.AddMilliseconds(ts.TotalMilliseconds);

        DateTime convertedDt = dt.ConvertToUnspecifiedDateTimeKind();

        convertedDt = convertedDt.ConvertBetweenTimeZones(sourceTimeZone, destinationTimeZone);

        return convertedDt.ToString("hh:mm:ss tt");

    }

    public static DateOnly ToDateOnly(this DateTime dateTime)

    {

        return new DateOnly(dateTime.Year, dateTime.Month, dateTime.Day);

    }

​

    public static TimeOnly ToTimeOnly(this DateTime dateTime)

    {

        return new TimeOnly(dateTime.Hour, dateTime.Minute, dateTime.Second, dateTime.Millisecond);

    }

​

    private static TimeZoneInfo GetEasternTimeZoneInfo()

    {

        TimeZoneInfo tz = RuntimeInformation.IsOSPlatform(OSPlatform.Windows)

           ? TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time")

           : TimeZoneInfo.FindSystemTimeZoneById("America/New_York");

​

        return tz;

    }

​

    private static TimeZoneInfo GetCentralTimeZoneInfo()

    {

        TimeZoneInfo tz = RuntimeInformation.IsOSPlatform(OSPlatform.Windows)

           ? TimeZoneInfo.FindSystemTimeZoneById("Central Standard Time")

           : TimeZoneInfo.FindSystemTimeZoneById("America/Chicago");

​

        return tz;

    }

​

    private static TimeZoneInfo GetPacificTimeZoneInfo()

    {

        TimeZoneInfo tz = RuntimeInformation.IsOSPlatform(OSPlatform.Windows)

           ? TimeZoneInfo.FindSystemTimeZoneById("Pacific Standard Time")

           : TimeZoneInfo.FindSystemTimeZoneById("America/Los_Angeles");

​

        return tz;

    }

​

    private static TimeZoneInfo GetServerTimeZoneInfo()

    {

        TimeZoneInfo tz = TimeZoneInfo.Local;

​

        return tz;

    }

    public static DateTime ConvertToUnspecifiedDateTimeKind(this DateTime dt)

    {

        return DateTime.SpecifyKind(dt,DateTimeKind.Unspecified);

    }

​

    public static DateTime ConvertBetweenTimeZones(this DateTime dt, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)

    {

        return TimeZoneInfo.ConvertTime(dt, sourceTimeZone, destinationTimeZone);

    }

}

​