Historical clue formulations

• Something a Eur. singer might embark on — 2021-02-16
• Series of bookings across America — 2020-11-11
• The Beatles had their last one in 1966 — 2018-05-26
• What a B'way show might have — 2005-11-24
• Pro golfers' circuit — 2005-08-04
• '64 event for the Beatles — 2001-03-16