copyright-regexp

copyright-regexp is a variable defined in `copyright.el'.
Its value is

"\\(©\\|@copyright{}\\|[Cc]opyright\\s *:?\\s *\\(?:(C)\\)?\\|[Cc]opyright\\s *:?\\s *©\\)\\s *\\(?:[^0-9\n]*\\s *\\)?\\([1-9]\\([-0-9, ';/*%#\n	]\\|\\s<\\|\\s>\\)*[0-9]+\\)"

Documentation:
What your copyright notice looks like.
The second \( \) construct must match the years.

You can customize this variable.