カレンダー日付を使ったバージョン番号管理ルール。 "CalVer is a versioning convention based on your project's release calendar, instead of arbitrary numbers." / Calendar Versioning — CalVer
"Spring Data 2020.0.0 (Codename: Ockham) is the first release train using the changed versioning scheme, previous release trains were identified by name, such as Neumann-RELEASE."