The volunteering, certification, course, honor, and publication lexicons required a strict datetime timestamp on their user-facing date fields, which rejected partial dates ("since 2018", year-only) and LinkedIn-importer writes. Drop format:datetime on startedAt/endedAt, issuedAt/expiresAt, completedAt, awardedAt, and publishedAt so they accept freeform YYYY-MM or YYYY-MM-DD strings, matching position, project, education, and involvement. Record metadata createdAt stays datetime.