"In 2011, federal debt had reached its legal limit on May 16, prompting then Treasury Secretary Timothy Geithner to declare a debt issuance suspension period, allowing certain extraordinary measures to extend Treasury's borrowing capacity. That debt limit episode was resolved on August 2, 2011, when President Obama signed the Budget Control Act of 2011 (BCA; S. 365; P.L. 112-25). The BCA included provisions aimed at deficit reduction and allowing the debt limit to rise in three stages, the latter two subject to congressional disapproval. Once the BCA was enacted, a presidential certification triggered a $400 billion increase, raising the debt limit to $14,694 billion, and a second $500 billion increase on September 22, 2011, as a disapproval measure (H.J.Res. 77) only passed the House. A January 12, 2012, presidential certification triggered a third, $1,200 billion increase on January 28, 2012, although the House passed a disapproval measure."
CRS Report for Congress, R43389
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html