GanttProject

Gantt Project is an open-source initiative whose purpose is to create a program that can produce graphs representing the distribution of tasks of a project in the short, medium, and long-term.

The diagram doesn't have to apply to the business world. You can create a diagram that distributes the time needed to prepare an exam, to build a home, or to carry out a specific task.

The program allows you to distribute the activities by person, or "resources", and it can also be used to manage group projects.

With Gantt Project you can test out the development of tasks and save a copy of their status as to when they will be executed so you can later compare them once they are finished.

This is tool is so complete that it even lets you set when each worker has days off as well as free days in general.