The S&P 500 just ended its longest stint in correction territory since 1984

The S&P 500 is back in business — at least for the moment. The broad-market benchmark ended its lengthiest period in correction territory in about 34 years, a move that may have bullish investors cheering and cracking open the bubbly.

On Wednesday, the S&P 500 Index SPX, +0.91%  soared 0.9% to 2,846.07, bursting above its Feb. 8 closing low of 2,851. Any finish above 2,839.10 would have officially marked a conclusion to the so-called correction. A decline of at least 10% from a recent top is typically how market technicians define an asset’s bearish corrective phase. A climb from its closing low of at least 10% is generally viewed as an emergence from out of correction.

As of Tuesday’s close, the S&P 500 had been in correction for 115 sessions, which was its longest such period since the 122-session period back in August 1984, according to WSJ Market Data Group.

Meanwhile, the Dow Jones Industrial Average DJIA, +0.68%   remains mired in correction. It logged its 116th straight session in correction, which marks its longest such bearish period also since August 1984. The Dow finished Wednesday’s trade up 0.7% at 25,414.

Separately, the Nasdaq Composite Index COMP, +1.17%   ended at an all-time high, representing its fourth in July, finishing up 1.2% at 7,932.24.

An impetus for stock moves on Wednesday were widely attributed to news that the U.S. and the European Union struck a tentative agreement to ease trade tensions that have dogged investors and undercut stock-market sentiment for months. President Donald Trump during a news conference with EU official Jean-Claude Juncker in the White House Rose Garden said that EU and the U.S. are working toward zero tariffs. Trump said the efforts were an effort to “make trade fairer and more reciprocal.”

—Ken Jimenez contributed to this article