A timeline is a visual representation of a list of events in chronological sequence.  It is usually a graphic design of a long bar with dates paralleling it and usually concurrent occurrences.
Timelines can use any appropriate scale to depict time that is appropriate for the subject and data; typically utilize a linear scale, in which a unit of distance equals a defined length of time. This timeframe is determined by the occurrences on the timeline. A timeline of evolution can span millions of years, but a timeline of the September 11th assaults can span minutes and an explosion can span milliseconds.