:hmm: Not sure why you posted the same question in two new threads, but anyway.
Open Basic.cfg and look for the SUBMARINEx blocks where x is a number 0 to 3. Change the Monthx and Yearx values to your taste.
That's the first bit. You then need to continue on through the file changing the availability date of conning towers and other equipment accordingly. No use giving yourself an XXI in 1939 if you have nothing to go with it.
