Change in Copyright Law
nBefore 1986: duration based on date of copyright or creation
nPrior 1989: notice required
nAfter: duration based on life of the author
nNow: life of the author plus 70 years
Why is copyright metadata “suddenly” needed? Because change in copyright law to base duration on the life of the author rather than counting from the date of copyright, means that the item itself does not contain the data you need to figure out if it is under copyright.
As originally enacted, the 1976 law prescribed that all visually perceptible published copies of a work, or published phonorecords of a sound recording, should bear a proper copyright notice. This applies to such works published before March 1, 1989. After March 1, 1989, notice of copyright on these works is optional. Adding the notice, however, is strongly encouraged and, if litigation involving the copyright occurs, certain advantages exist for publishing a work with notice.
Prior to March 1, 1989, the requirement for the notice applied equally whether the work was published in the United States or elsewhere by authority of the copyright owner. Compliance with the statutory notice requirements was the responsibility of the copyright owner. Unauthorized publication without the copyright notice, or with a defective notice, does not affect the validity of the copyright in the work.