National Guard and Reserve Retirement Modernization Act - Amends federal law concerning receipt of retired pay for non-regular service to provide that, in the case of a member of the Ready Reserve who serves on active duty after September 11, 2001, in support of a contingency operation or in response to a national emergency, retirement eligibility age shall be reduced below 60 by three months for each aggregate of 90 days during which the member so performs in any fiscal year after such date. Prohibits such retirement eligibility date from being reduced below age 50. Continues age 60 as the minimum eligibility age for DOD-authorized health care for such retirees.