CC-PDDC currently links to https://creativecommons.org/publicdomain/, but the actual license text is listed at https://creativecommons.org/publicdomain/certification/1.0/us/deed.en

This text has been listed as retired since 2010 by Creative Commons. Now that SPDX has both CC-PDM-1.0 and CC0-1.0, which are the Creative Commons recommended replacements, it seems like CC-PDDC should be moved to the Deprecated License Identifiers section.