Historical clue formulations

• Four-baggers — 2016-02-01
• Double doubles? — 2015-03-12
• Sends one out of the park — 2011-04-17
• Round-trippers, in sports lingo — 2011-03-13
• Smash hits — 2006-03-05
• They leave the park — 1999-01-29
• ← Season record for which 3-Down had this number — 1997-10-05
• Dingers, in sports lingo — 1997-08-16