April 21

From The Met Wiki

1963: The Mets sweep a doubleheader with 8-5 and 9-2 wins over the Braves at the Polo Grounds. The victories also give the Mets a sweep of the four-game weekend series.

1986: The Mets come from behind and pull out a 6-5 win over the Pirates at Shea Stadium.

1987: The Mets end a four-game losing streak with a 9-6 win over the Pirates at Pittsburgh. Rafael Santana hits a three-run homer and the Pirates turn a ninth-inning triple play.

1990: The Mets defeat the Montreal Expos, 5-4, at Shea Stadium. The Expos score three runs with two out in the ninth inning, but their comeback attempt falls short.