2026-05-01T15:39:36Z https://ssjda.iss.u-tokyo.ac.jp/Direct/oai2/ SSJDA Direct https://ssjda.iss.u-tokyo.ac.jp/Direct/oai2/ 2.0 admin@example.org 2026-04-17T09:54:26Z transient YYYY-MM-DDThh:mm:ssZ