Historical clue formulations

• One of two for a tee — 2020-10-25
• Sleeve opening — 2019-07-28
• Sometimes hard-to-find shirt opening — 2018-03-25
• What you might accidentally try to put your head through when getting into a sweater — 2017-01-12
• Opening on the side of a vest — 2016-03-08
• Vest opening — 2012-09-16
• Tee shirt opening — 2010-10-01
• Top opening — 2002-11-03
• Feature of 45-Down — 1999-06-19