This is only a simple example and I advise you to use TryParse instead of parse, but the example is sufficient to illustrate what to do:
static void Main()
{
DateTime d1 = DateTime.Parse("February 1, 2012");
DateTime d2 = DateTime.Parse("January 1, 2012");
if (DateTime.Compare(d1, d2) < 0)
{
Console.WriteLine("Everything OK!");
}
else
{
Console.WriteLine("Do what ever you see fit in the error case!");
}
}