Broke ground on January 15 1979. Opened November 15 1980.
EPCOT Center took 36 months from first blade of grass removed to official opening.
I guess many of us locals weren't fully aware of the construction until it reached a certain height. Life pre-interwebz, the kids will never know it. I was born on 11/24. I was able to ride it over Thanksgiving weekend that year. Thanksgiving was on 11/27, so I rode BTMRR on 11/28 or 11/29 1980. I'm sure we didn't head over there on Sunday. I'm getting old.