1. A computer-implemented method for managing project schedule data, the computer-implemented method comprising: a member schedule editor executing on a computer system and generating schedule data for a plurality of tasks in a project, wherein the schedule data for the plurality of tasks in the project includes data that identifies one or more started only tasks for which an actual start date has been specified but for which no actual end date has been specified, one or more planned only tasks for which a planned start or planned end date has been specified but for which no actual start date has been specified and one or more to-do list tasks for which no planned start date or planned end date has been specified, wherein the schedule data includes, for the plurality of tasks in the project, revision data and wherein the member schedule editor is configured to cause the schedule data to be displayed on a graphical user interface, wherein the graphical user interface displays the schedule data in a table organized in order of started only tasks, planned only tasks and to-do list tasks; wherein for each task of the plurality of tasks in the project, the revision data for the task has a revision data value from a set of revision data values that includes at least a first revision data value, a second revision data value, and one or more other revision data values, wherein the one or more other revision data values are not the first revision data value nor the second revision data value, wherein the first revision data value indicates that no current schedule data exists for the task and that the task is a to-do list task, wherein the second revision data value indicates that current schedule data exists for the task and that the current schedule data has not been revised for the task, and the one or more other revision data values indicate at least that schedule data exists for the task and that the schedule data has been revised for the task; the member schedule editor storing the schedule data in a current task schedule data structure; in response to detecting a change made to the schedule data for a task in the project, the member schedule editor causing the schedule data to be moved from the current task schedule data structure to a historical task schedule data structure that is separate from the current task schedule data structure, the member schedule editor generating revised schedule data that reflects the change made to the schedule data or the addition of new schedule data for the task in the project and the revised schedule data further includes an updated revision data value for the task, wherein the updated revision value is selected from a set of revision data values that includes at least the second revision data value and the one or more other revision data values, wherein the updated revision data value indicates that schedule data exists for the task in the project, and the member schedule editor causing the revised schedule data to be stored in the current task schedule data structure.