using System;

using System.Globalization;

public class Program

{

    public static void Main()

    {

        var fmt = "yyyy-MM-dd HH:mm:ss zzz";

        var date = "2016-12-29 09:58:07 +05:30";

        var val = DateTimeOffset.ParseExact(date, fmt, CultureInfo.InvariantCulture);

        System.Console.WriteLine(val.ToString(fmt));

    }

}

​

string errorMessage = rootCause.Message.Length > 4095 ? rootCause.Message.Substring(0, 4095) : rootCause.Message;