A timeline is a display of a list of events in chronological order. It is typically a graphic design showing a long bar labelled with dates paralleling it, and usually contemporaneous events.
Timelines can use any suitable scale representing time, suiting the subject and data; many use a linear scale, in which a unit of distance is equal to a set amount of time. This timescale is dependent on the events in the timeline. A timeline of evolution can be over millions of years, whereas a timeline for the day of the September 11 attacks can take place over minutes, and that of an explosion over milliseconds. While many timelines use a linear timescale—especially where very large or small timespans are relevant -- logarithmic timelines entail a logarithmic scale of time; some "hurry up and wait" chronologies are depicted with zoom lens metaphors.
There are different types of timelines:
There are many methods to visualize timelines. Historically, timelines were static images and were generally drawn or printed on paper. Timelines relied heavily on graphic design, and the ability of the artist to visualize the data.
Main article: List of timelines
Timelines are often used in education to help students and researchers with understanding the order or chronology of historical events and trends for a subject. To show time on a specific scale on an axis, a timeline can visualize time lapses between events, durations (such as lifetimes or wars), and the simultaneity or the overlap of spans and events.
Timelines are particularly useful for studying history, as they convey a sense of change over time. Wars and social movements are often shown as timelines. Timelines are also useful for biographies. Examples include:
Timelines are also used in the natural world and sciences, such as in astronomy, biology, and geology:
Another type of timeline is used for project management. Timelines help team members know what milestones need to be achieved and under what time schedule. An example is establishing a project timeline in the implementation phase of the life cycle of a computer system.
Timelines, no longer constrained by previous space and functional limitations, are now digital and interactive, generally created with computer software. Microsoft Encarta encyclopedia provided one of the earliest multimedia timelines intended for students and the general public. Hyperhistory and ChronoZoom are other examples of interactive timeline software.