A project is a set of tasks performed by resources. Tasks have a duration, with dependencies between them. When using a PM tool such as GanttProject, always remember to use the tool's capability to schedule the task, instead of entering the start and end dates. The ideal way to enter tasks is to enter the task name and its duration, and link to its predecessor or successor. The start and end dates are computed by the tool based on dependent tasks, their duration, resource availability during that time, and company working days.