using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var list = new List<string[]>() { new string[] { "09/04/2015" } };

        const string dateFormat = "d"; // e.g. "9/4/2015"

        List<string> dateList = list.Select(date => Convert.ToDateTime(date[0]).ToString(dateFormat)).ToList();

        foreach (var d in dateList)

        {

            Console.WriteLine(d);

        }

    }

}