# Bitemporal ledger

A ledger that keeps at least two time axes per record. Ledgerbook keeps exactly three: effective time (when the event happened), insertion time (when the ledger recorded it) and knowledge time (what was believed, and when) — recorded and believed are different axes.

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