using System;

using System.Web;

public class Program

{

    public static void Main()

    {   

        DateTime dateTime;

        var url = "https://websurveys2.servmetric.com/theme/sm/2055?&reference=z0JznBN&Q_EventDateTime=2018-10-15+16%3a01%3a09&Q_LOCATION=107&SERVICE=Benefits&Q_NUM_TO=07515355326";

        var qry = HttpUtility.ParseQueryString(url);

        var dateTimeStr = qry["Q_EventDateTime"];

        if(DateTime.TryParse(dateTimeStr, out dateTime)) {

            Console.WriteLine("Done!: {0}", dateTime);

        } else {

            Console.WriteLine("Nope :(");

        }

    }

}