Generally.
The passage of time does not cure the illegality of a sign which was
built, installed, modified, altered or erected in violation of the
relevant rules then in effect.
All advertising structures, signs or accessory signs which do
not conform to the provisions of this chapter, but which were constructed
in compliance with previous regulations, ordinances, resolutions or
other conditions of approval, shall be regarded as legal nonconforming
and may remain as permitted by this chapter, except as specified in
this chapter.