Update documentation for Roadmap date ranges

doc/user/group/roadmap/index.md

@@ -10,12 +10,35 @@ shows such a visualization for all the epics which are under a group and/or its
 
 ## Timeline duration
 
-![roadmap timeline](img/roadmap_timeline.png)
+Starting with [GitLab Ultimate][ee] 11.0, Roadmap supports three different date ranges; Quarters, Months (Default) and Weeks.
 
-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.
+### Quarters
+
+![roadmap date range in quarters](img/roadmap_timeline_quarters.png)
+
+In _Quarters_ preset, roadmap shows epics which have planned start or finish dates _falling within_ or
+_going through_ **past quarter**, **current quarter** and **next 4 quarters**, where _today_
+is shown by the vertical red line in the timeline. The sub-headers underneath the quarter name on
+the timeline header represent the month of the quarter.
+
+### Months
+
+![roadmap date range in months](img/roadmap_timeline_months.png)
+
+In _Months_ preset, roadmap shows epics which have planned start or finish dates _falling within_ or
+_going through_ **past month**, **current month** and **next 5 months**, where _today_
+is shown by the vertical red line in the timeline. The sub-headers underneath the month name on
+the timeline header represent the date on starting day (Sunday) of the week. This preset is
+selected by default.
+
+### Weeks
+
+![roadmap date range in weeks](img/roadmap_timeline_weeks.png)
+
+In _Weeks_ preset, roadmap shows epics which have planned start or finish dates _falling within_ or
+_going through_ **past week**, **current week** and **next 4 weeks**, where _today_
+is shown by the vertical red line in the timeline. The sub-headers underneath the week name on
+the timeline header represent the days of the week.
 
 ## Timeline bar for an epic