If the difference between Date acquired and Date sold is greater than one year, the gain or loss is long-term. If a year or less, it's short-term.
Generally, if box 2 is empty, then the Date acquired and Basis are unknown. In that case, when entering the data in TurboTax, for Sale category, select Box D (long term noncovered). Regulations requiring brokerage firms to report the purchase price changed in 2011, so these would all be long-term transactions.
