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
1. The distinction between modern and pre-modern is a bit shaky at times. The most common dispute about when “modern” history begins is whether it starts right before or right after the Middle Ages (being named as such because they fall between Classical history and Modern history). Ultimately the distinction between modern and pre-modern is fairly arbitrary, especially when applied to places outside of Europe.
Beginning with the Earth’s formation, through to the beginning of the modern day, fan favorites like ancient Egypt, Babylon, Harappa, Rome, and Aksum make their debuts. Though they have a less direct impact on the world today, these historic cultures held major influence over the course of history. The inventions of agriculture, fire, megalithic construction, and speech are the foundations of human life, as well as the development of the arts and sciences. Check out our timelines to discover more about these remote (and often unrecognizable) times.
This timeline presents significant events and developments in the innovation and management of information and documents from cave paintings (ca 30,000 BC) to the present. To keep recent electronic developments from dominating the listing, only the most significant digital innovations are included.
Here is the key to the icons used in the timeline:
This is not a trick question: what is a historical timeline? Maybe you have some idea. Maybe you remember being in school and seeing in your textbook a line dotted with important dates and terms. For many, this is probably the image that comes to mind.
A historical timeline is a method of highlighting important historical dates, terms, figures, and events in a chronological fashion. Historical timelines can be very broad or very specific. For example, a massive and broad historical timeline might deal with the whole of human history, marking important dates and eras, while a specific timeline might deal with just a few years, such as World War II between 1939-1941. Some timelines might relate to only political events, while others might include only wars. So you can see, timelines are customizable. They can be created for custom purposes. The possibilities for timelines are nearly endless: a timeline of the French Revolution, a timeline of the Great Depression, a timeline of the Soviet Union, and so on and so forth.
earliest monuments: pyramids (Egypt)
first diagnosis of AIDS (USA, 1981) → identification of HIV (1984), global epidemic killing 32 million, continuing health risk