In most voyage charters, the charterer is allowed by the shipowner a certain amount of time within which to load and/or discharge the cargo. This time is known as laytime. It can be expressed as a number of tonnes per day, a number of tonnes per (workable) hatch per day or simply a number of hours or days. There are periods when laytime does not count; these may be weekends, public holidays or bad weather depending on the particular charter-party. Once laytime has been used up, the charterer is very often liable for demurrage, an agreed sum of money paid for every extra day taken to load or discharge the cargo.