String - I get a Format Exception, because "YYYY" is not a known format code: it should be:
String strDate = "24/01/2013 00:00:00";
DateTime date = DateTime.ParseExact(strDate, "dd/MM/yyyy HH:mm:ss", CultureInfo.InvariantCulture);
Console.WriteLine(date);
Which gives me:
24/01/2013 00:00:00
I suspect your output is formatting the data to 12 hour (AM/PM) format instead:
Console.WriteLine(date.ToString("dd/MM/yyyy hh:mm:ss"));
So try:
Console.WriteLine(date.ToString("dd/MM/yyyy HH:mm:ss"));
Which might be misleading you.