Excerpt from 99 Tips and Traps for Microsoft Office Project by Paul Harris of Eastwood Harris
The Gantt Chart Wizard, available by clicking on the icon or selecting Format, Gantt Chart Wizard…., is a straightforward method of formatting your bars but will not format and display the Negative Float (Slack) and Free Float (Slack) bars. These will have to be added manually using the Bar Style form by:
- Selecting Format, Bar Styles…, or double-click anywhere in the Gantt Chart area except on an existing bar (this will open the Format Bar form to format an individual bar).
Then add two additional bars as indicated below:
- Negative Float is generated when the Late date is calculated earlier than the Early date and represents the amount of time that the schedule must catch up or how much earlier a project must start to finish on time. Setting a Late constraint or Deadline date earlier than the calculated Early Finish date normally causes Negative Float.
- Free Float is the amount of time a task may be delayed without delaying a successor task.
Note: Unlike some other some software, the Negative Float is drawn from the Start Date of a task and not the Finish Date. Therefore one bar is required for Negative Float and one for Positive Float.