Definitions of dateless:

• adjective:   unaffected by time

  Example: "Few characters are so dateless as Hamlet"

• adjective:   not bearing a date

  Example: "A dateless letter"

• adjective:   of such great duration as to preclude the possibility of being assigned a date

  Example: "Dateless customs"

• adjective:   having no known beginning and presumably no end

  Example: "The dateless rise and fall of the tides"