Happy Birthday: The compact disc has been around for four decades

[Redaktion]

Although it became commercially available more than three years later, the compact disc as we know it was demonstrated for the international press by Philips on March 8, 1979. Later that month, Sony joined in and the two companies quickly managed to turn the CD format into a global standard and bring this technology to the masses.

https://www.notebookcheck.net/Happy-Birthday-The-compact-disc-has-been-around-for-four-decades.413721.0.html

[Soundboy]

Compact disc didn't become available to the general public, at least in Japan, until October 1, 1982.  Fifty titles were released by CBS/Sony of Japan (now Sony Music).  Until a product reached the general public, I don't think time during the developmental stages should be counted.