Data is only subject to the GDPR if it has a personal reference. If the date (singular of data) allows conclusions to be drawn about an identified or identifiable natural person, the personal reference is established. It is sufficient if the mere possibility of identification exists.
A person can be determined or identified directly or indirectly. Directly identifiable and thus determinable, a natural person is mainly through his name. In many cases, the name alone is not sufficient for identification; other identification features must be used, such as date of birth, e-mail or postal address, social security number or tax identification number.
A person is indirectly identifiable if there is a personal datum, but it cannot be directly assigned to a person. This is also the case if the data does not immediately allow a conclusion to be drawn about a specific person. However, the person can be determined by this data because the information can be used with other information to distinguish or identify the person.
Examples
Direct: Surname, first name, date of birth
Indirect: IP address –> owner of the IP address –> surname, first name stored with the network operator.
However, there is also a limitation here. If no personal reference can be established with a reasonable or appropriate use of resources (time, monetary resources, currently available technologies), a person is not identifiable.
A date is also not personal or personal-relatable if it is effectively anonymized.