Conversation so far:
When did Richard Stallman attend Harvard?
Richard Stallman was a first-year student at Harvard University in fall 1970.
What did Richard study at Harvard?
Stallman received a bachelor's degree in physics (magna cum laude) from Harvard in 1974.
Did Richard Stallman do any research at Harvard?
Did anything notable happen with Richard Stallman at Harvard?
In 1971, near the end of his first year at Harvard, he became a programmer at the MIT Artificial Intelligence Laboratory, and became a regular in the hacker community.

Question: when did he enroll to MIT?
Self-contained rewrite: When did Richard Stallman enroll to MIT?