How to set date format in a connection to SQL?

In Microsoft SQL Server Management Studio, after calling the stored procedure, I can see that the time has the format 2011-05-20 19:56:09 in table.

However, in my C# program, after using an OdbcConnection to get the record from the table, I find that the time is in the format 05/20/2011 19:56:09. So I manually convert the format MM/DD/YYYY hh:mm:ss to YYYY-MM-DD hh:mm:ss (Actually, how do I verify the format is h or HH since the hour shown is 19?).

My question is why and in which part of connection, the format is changed? How can I set invarient culture in my connection?

cmd = new OdbcCommand("{?=CALL stored_procedure_in_SQL(?,?)}", m_SqlConn);
cmd.Parameters.Add(new OdbcParameter("RETURN_VALUE", OdbcType.Int, 4,
    ParameterDirection.ReturnValue, false, 0, 0, null, 
    DataRowVersion.Default, null));

//@parameter1
cmd.Parameters.Add("@parameter1", OdbcType.VarChar, 50).Value = value1;

//@parameter2
cmd.Parameters.Add("@parameter2", OdbcType.Int)=value2;

object objTime=ds.Tables[0].Rows[0][0]
Console.WriteLine(objTime.Tostring()) //05/20/2011 19:56:09
DateTime dateTime = Cdate(objTime, "MM/dd/yyyy h:mm:ss tt"); 
//2011-05-20 19:56:09 
Console.WriteLine(dateTime.ToString("yyyy-MM-dd HH:mm:ss")); 

//Function Cdate
static public DateTime Cdate(object val, string format)
{
    // check if the object is a date time alread
    string str;
    if(val is DateTime)
    {
        // Since val is already a dateTime,Return here
        return (DateTime)val; 
    }

    // convert via string
    if(val != DBNull.Value)
    {
        str = val.ToString().Trim();
    }
    else
    {
        str = "";
    }

    if(str == "")
    {
        return DateTime.MinValue;
    }
    else
    {
        return DateTime.ParseExact(str, format, 
            CultureInfo.InvariantCulture);
    }
}