Wall Street romped to records Thursday as a delayed jubilation swept markets worldwide following the Federal Reserve’s big cut to interest rates. The S&P 500 jumped 1.7% for one of its best days of the year and topped its last all-time high set in July.

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.

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