A time book is a mostly outdated accounting record, that registered the hours worked by employees in a certain organization in a certain period. These records usually contain names of employees, type of work, hours worked, and sometimes wages paid.

In the 19th and early 20th century time books were separate held records. In those days time books were held by company clerks or foremen or specialized timekeepers. These time books were used by the bookkeeper to determine the wages to be paid. The data was used in financial accounting to determine the weekly, monthly and annual labour costs, and in cost accounting to determine the cost price. Late 19th century additional time cards came in use to register labour hours.

Nowadays the time book can be a part of an integrated payroll system, or cost accounting system. Those systems can contain registers that describe the labour time spend to produce products, but those registers are not regularly called time books, but timesheets.

Before the 19th century employees could be registered on a payroll, especially in cases such as crewmembers on a ship or soldiers stationed in a location. The paid wages were noted in daybooks, in which daily expenses were registered, and eventually in the other accounts in the bookkeeping systems.

In the 19th century when organizations started to grow a separate register of labour hours emerged, which was called a time book. There were used to keep account of the work done. Loudon (1826) explained, that in gardening the books necessary for the system of keeping accounts are, the time-book, the cash-book, and the forest or plantation book. Loudon described how time books were handled in those days:

The master inserts the name of every hand; and the foreman of each department inserts the time in days, or proportions of a day, which each person under his care has been at work, and the particular work he or she has been engaged in.
At the end of each week the master sums up the time from the preceding Saturday or Monday, to the Friday or Saturday inclusive; the sum due or to be advanced to each man is put in one column, and when the man receives it he writes the word received in the column before it, and signs his name as a receipt in the succeeding column.
The time-book, therefore, will show what every man has been engaged in during every hour in the year for which he has been paid, and it will also contain receipts for every sum, however trifling, which has been paid by the gardener for garden-labour.

And furthermore:

In short, it would be difficult to contrive a book more satisfactory for both master and servant than the time-book, as it prevents, as far as can well be done, the latter from deceiving either himself or his employer, and remains an authentic indisputable record of work done, and of vouchers for money paid during the whole period of the head gardener's services.
In laying out grounds in a distant part of the country, where upwards of two hundred men were employed under one foreman, we have had their time, employment, and payments recorded, and receipts taken, in this way, and found it an effectual bar to every thing doubtful or disagreeable.