# Period

A calendar construct with open, soft-closed, closed and reopened states that governs which writes are legal; period states and close gates ship at PH-1.

- Source: [Ledgerbook glossary](/glossary/)
- Related: [Accounting data layer](/glossary/accounting-data-layer/), [Ledger of record](/glossary/ledger-of-record/), [Bitemporal ledger](/glossary/bitemporal-ledger/)