(Date.new(2020,1,1) .. Date.new(2020,1,10)).overlaps?(Date.new(2020,1,10) .. Date.new(2020,1,20))
=> true

(Date.new(2020,1,1) ... Date.new(2020,1,10)).overlaps?(Date.new(2020,1,10) ... Date.new(2020,1,20))
=> false