Historical clue formulations

• Yanks' rivals — 2019-12-07
• Fenway Park team, familiarly — 2012-03-27
• Yanks' foes — 2011-01-01
• Green Monster's squad — 2010-11-26
• Bronx Bombers' foes — 2010-03-11
• Beantown team, briefly — 2004-09-14