According to Reuters, the Dow Jones and the S&P closed their best June in decades ahead of the G20 summit.On June 28th, the Dow Jones Industrial Average and the S&P 500 ended the month trading up between 6-and-7 percent.That marks the best June for the S&P since 1955, and the best June for the Dow Jones since 1938.On the day, the Dow added about 73-points rising to 26,599, while the S&P tacked on 16-points, bringing the benchmark index to 2,941.