Stocks delivered their biggest single-day gains of the summer on Monday, as tensions between the U.S. and North Korea appeared to wane for the time being. The Dow Jones Industrial Average (DJINDICES: ^DJI) enjoyed a triple-digit gain to close just shy of the symbolic 22,000 level, while the S&P 500 (SNPINDEX: ^GSPC) and Nasdaq Composite (NASDAQINDEX: ^IXIC) each fared even better.