According to data put together by Harvard's Amitabh Chandra, which the New York Times published in raw form in 2006, it was the least common birth date for more than two decades in the late 20th century; September 16 comes in at the other end of the spectrum, as the most common date for babies to be born.
A Goldfish will grow quicker if you increase its metabolism slightly. This can be done by keeping the water at summer temperatures of around 65F to 70F. Goldfish kept at this higher temp will also need added space (2 gals per inch of fish), air bubbles and a really good filtration system.
A more common size would be about 12 inches for a common and about 8 to 10 inches for a fancy. They will grow faster, but not necessarily ultimately larger, in large ponds than in aquaria. People who say they get to be three feet long probably have goldfish confused with koi or other carp.