Return result from getdate function from sql to c# give wron

Hi guys i have windows form application in this form i need to show date of server 

not date of client so that i write following function 

stored procedure 

create proc datetoday1
as
select getdate()as datetoday

function in c#

public string GetDateProcesses(string ConnectionString)
{
SqlConnection con = new SqlConnection(ConnectionString);
SqlCommand cmd = new SqlCommand();
cmd.Connection = con;
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandText = "datetoday1";
con.Open();
string getdate=Convert.ToString(cmd.ExecuteNonQuery());
con.Close();
return getdate;
}

in interface 

but it return -1 not date of server what is wrong in my code

and what modification in code to return true result