The Final Score

On June 15, 1977, the Mets traded Tom Seaver to the Reds for Pat Zachry, Doug Flynn, Steve Henderson and Dan Norman.

But on June 15, 1983, the Mets acquired Keith Hernandez from the Cardinals for Neil Allen and Rick Ownbey.

BTW, June 15 is also the anniversary of the day the Giants cut Phil Simms in 1994.

Oh,and in 1957 the Yankees traded Billy Martin (and Ralph Terry, Woodie Held and Bob Martyn) to the Kansas City Athletics for Ryne Duren, Jim Pisoni and Suitcase Simpson, but that doesn't count because the A's were operating as a Yankees farm team at the time.