Daybook is a term used to refer to a type of bookkeeping system. It is a combination of a CALENDAR, DIARY, and LEDGER. A CALENDAR is a system of organizing days for social, religious, commercial, or administrative purposes. A DIARY is a record of events, experiences, and observations kept regularly over a period of time. A LEDGER is an accounting record of financial transactions. Together, these three components form the daybook, which is used to keep track of financial transactions and other important information.