I try to setup a harvest client for a generic oai-pmh server, using oai_dc metadata format.
For datasets before 2021, year in the citation text is always 2021:

I found that for a harvested dataset, the date used is the distribution date or harvesting date if undefined:

https://github.com/IQSS/dataverse/blob/develop/src/main/java/edu/harvard/iq/dataverse/DataCitation.java#L714

But this date is not set for an harvested dataset, only the publication date is set

https://github.com/IQSS/dataverse/blob/develop/src/main/resources/db/migration/afterMigrate__1-7256-upsert-referenceData.sql

Ex:

https://dataverse.harvard.edu/dataverse/harvard?q=&fq2=publicationDate%3A%222012%22&fq0=dvObjectType%3A%28datasets%29&fq1=metadataSource%3A%22Harvested%22&types=datasets&sort=dateSort&order=