There is a difference between the interpretation of the phrase "personal data" within the context of the GDPR and outside the context of GDPR. At least I think there is a difference.

For example, consider a website that maintains a collection of birthdays for public figures derived from public sources (historical documents, news accounts, social media posts from the public figures themselves, etc.). In many jurisdictions the birth dates might even be available via public record searches.

Clearly the birth dates are "personal data" in the colloquial sense of the phrase, but I don't think that the data as held by the website operator would be subject to the GDPR provisions, right?