Create Milestone

Use JIRA's "create issue" button to create a milestone:

All you need to do is entering a project, issue type (may be, you have an own issue type specified for milestones), due date and Gantt Options: please click on the check box "Milestone".

Viewing the new created issue, it should look like the following sample: its planned start and end date is set equal to its due date, automatically.

On the Gantt-Chart, this milestone is presented by a diamond (milestone icon) in green or red color: