Eight days in winter marking the temple's recovery — the feast Jesus is at in John 10.
The Feast of Dedication remembers the cleansing and rededication of the temple after it had been desecrated, two centuries before the New Testament. It is not in the Old Testament, because the events it marks happen after the last of those books; it reaches the Bible only as a date in John, who mentions in passing that it was winter. Later Judaism keeps it as Hanukkah.
Not a word scripture uses. No law appoints it and the Old Testament never mentions it — the events it marks fall between the Testaments. John 10:22 is the only place in the Bible it appears, as the setting for a conversation.