By default, the OverviewShowMarkTimeZones property is False. The OverviewVisible property indicates whether the control's overview part is shown or hidden. The MarkTimeZone method highlights different time-zones. Use the OverviewShowMarkTimeZones property to show the marked time-zones on the control's overview map. The color for the time-zone is being indicated by the Color parameter of the MarkTimeZone method. The time-zone is being shown only if the start and end dates points to a valid date, the Color is different then chart's background color ( BackColor property ), and the pattern for the time-zone is not empty. If the time-zone displays HTML captions they do not appear on the overview part of the control. A time-zone may be shown in the overview part of the control only if the Color parameter is the same as BackColor property, and the OverviewBackColor property is different than the chart's BackColor property.The OverviewShowSelectDates property specifies whether the selected dates are shown in the overview part of the control. 

The following screen shot shows time-zones in the overview map: