class Program
{
    static void Main(string[] args)
    {
        var result = UnixTimeStampToDateTime(1497528525420);
    }
    public static DateTime UnixTimeStampToDateTime(double unixTimeStamp)
    {
        var dtDateTime = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
        dtDateTime = dtDateTime.AddMilliseconds(unixTimeStamp).ToLocalTime();
        return dtDateTime;
    }
}