I activated an ATM card once and the automated system told me for a PIN "Many of our customers are choosing their mother's birthday, please enter the month and

I activated an ATM card once and the automated system told me for a PIN "Many of our customers are choosing their mother's birthday, please enter the month and day your mother was born." So, out of a keyspace of 10,000, they were shoehorning most of their users into a space of 365(366). I tried to enter something that was not a valid 4 digit date and the system rejected it. I had to call back and talk to a customer service rep to get a non-date PIN.