These changes relate to the deadline for issuance of contrarian instructions concerning option exercise on the expiration date for all CME and CBOT domestic options on Equity Index futures. The rule changes clarify that an option will be automatically exercised, in the absence of contrarian instructions issued to the clearing house by 7:00 p.m., on expiration day. The current rule indicates that contrarian instructions must be issued by 7:00 p.m. on the day after expiration day. These amendments are designed to align the rulebook language with current operational procedures. The effective date for these modifications to CME and CBOT options on Equity Index futures exercise will be Tuesday, March 12, 2013, for the trade day ending Wednesday, March 13, 2013.