Copyright laws have been changed several times since the 19-70's. Works registered prior to January first, 19-78 were eligible for a copyright protection period of 28 years. They could be renewed for another 28. Since 19-78, the renewal period was extended to 47 years for a total of 75. In 19-92, the law was changed again, making the renewal automatic. For works created after 1978, the new copyright period is for the author's life plus 50 years. In the case of two or more authors, the copyrights extend 50 years beyond the death of the last surviving collaborator. Finally, works for hire are protected for either 75 years after the date of publication or 100 years after creation, whichever is shorter.