The calculation period defines the service life of the building. All the impacts are calculated over this period.
Not all calculation tools have this query available. For some tools, the calculation period is defined by the certification scheme requirements and is not editable by the user.
To add or edit your calculation period, click 'Input data' and open the 'Calculation period' query. Enter the desired calculation period (also known as the service life of the building) as required by the client or by regulation. If no required service life is defined, you can use the service life intended by the designer.
You can read further about building product service lives here.