For all the nail-biting about the economy over the past year, investors had it easy: a 5% yield on short-term U.S. debt, one of the safest investments in the world. Now, the times they are a-changin’—again.

Wall Street is roaring toward records Thursday as a delayed jubilation sweeps markets worldwide following the Federal Reserve’s big cut to interest rates. The S&P 500 was 1.5% higher in early trading and above its all-time closing high set in July.

"This would be the third time that stocks entered a cycle where annual returns compound at high teens," Fundstrat's Tom Lee said.