Wow, something strange happened. I started the 4th patrol on April 26th, like I said above, however, half way out of the harbor the game crashes. I restart it, but now the date is March 18th, 1940. I start the 4th patrol again, but when I started leaving the harbor I checked the clock and it shows February 26th, 1940. Very strange, I'm traveling back in time
Most likely another bug.