February 29 is a date that usually occurs every four years, and is called leap day. This day is added to the calendar in leap years as a corrective measure, because the Earth does not orbit around the sun in precisely 365 days. The Gregorian calendar is a modification of the Julian calendar first used by the Romans.
The Strategic Defense Initiative (SDI), also known as Star Wars, was a program first initiated on March 23, 1983 under President Ronald Reagan. The intent of this program was to develop a sophisticated anti-ballistic missile system in order to prevent missile attacks from other countries, specifically the Soviet Union.