Wall Street pros are confidently calling the bottom of the 2002 market - based on what happened in 1974. 

That's the last time U.S. stocks were in a long-term bear market, offering lessons about today's markets. 

The 1974 bear market bottomed out after the S&P 500 index had lost roughly 48 percent of its value. That is about exactly where the S&P stands today, giving some market commentators reason to believe the 2002 market is also at - or near - its bottom. 

With the big rallies Monday and last Wednesday, the S&P experienced is biggest four-day percentage increase since 1974. The four-day rally in 1974 came just after the bottom. 

"This is exactly how a bottom acts," said Jeff Van Harte, portfolio manager at the Transamerica Premier Equity fund. "The selling sizzles out and the mutual fund managers start putting new money to work." 

Van Harte, who was just starting his career on Wall Street during that last bear market, had other lessons to learn from those times. 

"In 1974, you had big rallies like this and people though it was a big head fake," he said. "But it turned out that it was real. If you got in then at the bottom, you got 15 percent almost immediately and 15 percent annual reutrns for years afterwards." 

That's why Van Harte says investors with long-term investment horizons should put money to work in the market - now. 

"You don't want to miss out on the upside from the bottom," he said. "I think that's why we're seeing a lot of buying."