N.Y.C. Admin. Code § 27-388: § 27-388 Retroactive provisions.

Except as otherwise provided, the provisions of this subchapter are not retroactive except that the provisions of this article and article nine of subchapter six of this chapter for certain existing office buildings are retroactive. Signs required by this article must be installed no later than March sixth, nineteen hundred sixty-nine. Where auxiliary systems for emergency exit lighting are to be provided, the installation must commence no later than May sixth, nineteen hundred sixty-nine.