https://www.thetimes.co.uk/travel/where-was-i/ The slender monument commemorating the successful departure in 1620: https://historicengland.org.uk/services-skills/education/educational-images/pilgrim-fathers-memorial-southampton-6346 Tonight is the 110th anniversary of the night that the voyage of the second departure came to...
As mentioned in the last paragraph, the date of the puzzle is the anniversary of the second departure. Look up historic events that happened on that day.