This setting relates to the Project lines - planning form, on which you can enter and change planning data. If the Calculate project planning check box is selected, the planning is calculated as soon as one of the planning fields, such as the start or end date, has been changed. Leave this check box empty to allow the planning to be calculated only when you manually start the calculation.

If you often work with large projects, you are recommended not to enable the setting and to manually start the planning calculation by using the Execute project planning option. When you are dealing with large projects, the process can take quite some time.