Timeline charts are single-series charts that illustrate periods of times. This is usually done using horizontal bars, and a datetime horizontal baseline. The other axis contains the objects or categories associated with each start-end interval. These could be some tasks or activities. Timelines are similar to range bar charts with a datetime X axis. Unlike Gantt charts, timeline charts do not show task dependencies and other details.
Our Project Activities single-series demo charts show datetime start-end intervals for some project's activities. They look like range bar charts with a datetime axis. And some of them are emulated indeed with range charts, when there is no native support.