Array Sequence TimeStamp Validation

Question

I am getting an error below that the string is not a valid datetime format. Can someone help below.

using System;

using System.Linq;

using System.Text.RegularExpressions;

class Test

{

    static void Main()

    {

       string[] ArrayElement = new string[6];

       ArrayElement[0]= "1:05:00 PM 06/25/2013 On True";

       ArrayElement[1]= "1:10:00 PM 06/25/2013 Off True";

       ArrayElement[2]= "1:15:00 PM 06/25/2013 On True";

       ArrayElement[3]= "1:20:00 PM 06/25/2013 Off True";

       ArrayElement[4]= "1:25:00 PM 06/25/2013 On True";

       ArrayElement[5]= "1:30:00 PM 06/25/2013 Off True";

 

       Console.WriteLine(Validate(ArrayElement)); // True  

       ArrayElement[2]= "1:15:00 PM 05/25/2013 On True";

       Console.WriteLine(Validate(ArrayElement)); // False  

       Console.ReadKey();  

    }

    static bool Validate(string[] state)

    {

       string f = "h:mm:ss tt MM/dd/yyyy";

 

       // extract time stamps and make sure they're in sequence

       DateTime[] stamps = state

       .Select(s => DateTime.ParseExact(s.Substring(0, s.LastIndexOf(" ")), f, null)).ToArray();

       for(int i = 1; i < stamps.Length; i++)

       {

           if(stamps[i] < stamps[i-1]) return false;

       }

       // extract On/Off's and validate them

       state = state.Select(s => s.Substring(s.IndexOf("O"))).ToArray();

       string text = String.Join("", state);

       string regExp = "^(OnOff)+$";

       return Regex.IsMatch(text, regExp);

    }

}