Introduced in GitLab Ultimate 10.5.
An Epic within a group containing Planned start date and/or Planned finish date can be visualized in a form of a timeline (e.g. a Gantt chart). The Epics Roadmap page shows such a visualization for all the epics which are under a group and/or its subgroups.
Roadmap shows epics which have planned start or finish dates falling within or going through the past 3 months or next 3 months from today, where today is shown by the vertical red line in the timeline. The dates underneath the month on the timeline header represent the starting day (Sunday) of the week.
The timeline bar indicates the approximate position of an epic based on its planned start and finish date. If an epic doesn't have a planned finish date, the timeline bar fades away towards the future. Similarly, if an epic doesn't have a planned start date, the timeline bar becomes more visible as it approaches the epic's planned finish date on the timeline.