C# Convert UTC to TimeZone or Vice Versa

TimeZone.cs

public static DateTime ToTimeZoneTime(DateTime time, string timeZoneId = "UTC")
{
    TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById(timeZoneId);
    return TimeZoneInfo.ConvertTimeFromUtc(time, tzi);
}

public static DateTime ToUTC(DateTime time, string timeZoneId = "UTC")
{
    TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById(timeZoneId);
    return TimeZoneInfo.ConvertTimeToUtc(time, tzi);
}

public static Void ListTimeZones()
{
  //Reference: https://support.microsoft.com/en-ae/help/973627/microsoft-time-zone-index-values
  foreach (TimeZoneInfo z in TimeZoneInfo.GetSystemTimeZones())
  {
    Console.WriteLine(z.Id);
  }
}

var startDateTime = DateTime.UtcNow;
var _timeZoneId = "Arabian Standard Time";

var convert = ToTimeZoneTime(startDateTime, _timeZoneId).ToString("yyyy-MM-dd"); // Convert UTC to Time Zone Time