The present invention relates to designating that durations of specific tasks are estimated or tentative. The user can indicate estimated durations by the sheet mode or the dialog mode. Estimated duration characters are symbols of uncertainty, such as “?”, that indicate that the duration entries are not fixed and final, but may need to be adjusted in the future. The user can select an option to not display the estimated duration character even though the estimated field for the task is set. The user can also select an option to have new tasks that are created have estimated duration characters until the user chooses to enter a duration value. The program can also filter the task list to display only tasks that have estimated duration characters.