Your second midterm today will be available at approx. 12:05 PM. You will have one hour to complete it, and you can use any 60-minute block of time that ends before the closing time, 11:59 PM tonight.
P.S. Don't forget that, while I am putting last minute changes to things, the exam might temporarily disappear and reappear a few times between now and lunchtime. Do not panic!