17 files declare their use of SchemaDateBase in Schema.org Metatag 8

SchemaArticleDateModified.php in schema_article/src/Plugin/metatag/Tag/SchemaArticleDateModified.php

SchemaArticleDatePublished.php in schema_article/src/Plugin/metatag/Tag/SchemaArticleDatePublished.php

SchemaEventDoorTime.php in schema_event/src/Plugin/metatag/Tag/SchemaEventDoorTime.php

SchemaEventEndDate.php in schema_event/src/Plugin/metatag/Tag/SchemaEventEndDate.php

SchemaEventPreviousStartDate.php in schema_event/src/Plugin/metatag/Tag/SchemaEventPreviousStartDate.php

SchemaEventStartDate.php in schema_event/src/Plugin/metatag/Tag/SchemaEventStartDate.php

SchemaJobPostingDatePosted.php in schema_job_posting/src/Plugin/metatag/Tag/SchemaJobPostingDatePosted.php

SchemaJobPostingValidThrough.php in schema_job_posting/src/Plugin/metatag/Tag/SchemaJobPostingValidThrough.php

SchemaMetatagTestDate.php in tests/modules/schema_metatag_test/src/Plugin/metatag/Tag/SchemaMetatagTestDate.php

SchemaMovieDateCreated.php in schema_movie/src/Plugin/metatag/Tag/SchemaMovieDateCreated.php

SchemaPersonBirthDate.php in schema_person/src/Plugin/metatag/Tag/SchemaPersonBirthDate.php

SchemaRecipeDatePublished.php in schema_recipe/src/Plugin/metatag/Tag/SchemaRecipeDatePublished.php

SchemaReviewDatePublished.php in schema_review/src/Plugin/metatag/Tag/SchemaReviewDatePublished.php

SchemaSpecialAnnouncementDatePosted.php in schema_special_announcement/src/Plugin/metatag/Tag/SchemaSpecialAnnouncementDatePosted.php

SchemaSpecialAnnouncementExpires.php in schema_special_announcement/src/Plugin/metatag/Tag/SchemaSpecialAnnouncementExpires.php

SchemaVideoObjectExpires.php in schema_video_object/src/Plugin/metatag/Tag/SchemaVideoObjectExpires.php

SchemaVideoObjectUploadDate.php in schema_video_object/src/Plugin/metatag/Tag/SchemaVideoObjectUploadDate.php