File:Time relations chart.jpg

English: This chart shows the relations between common units used to measure time: the millisecond, second, minute, hour, day, week, month, Gregorian calendar year, decade, century, and millennium. It also includes some lesser-known units with historical or scientific uses, as well as the actual definitions for more colloquially indefinite timespans: the Planck time, jiffy in physics, Svedberg, jiffy in electronics, moment, fortnight, lunar month or lunation, quarantine, quarter, tropical year or solar year, olympiad, lustrum, indiction, and eon. Units of metric time, such as a hectosecond, were not included, but the millisecond was included because of its frequent use.

The shorter units of time are at the bottom of the chart and duration increases as you go up, but it should be noted that the chart is not drawn to scale as these units are of wildly varying durations. Also, some of the conversions are averages based on units of variable lengths (for example, there are 30.4 days in one month on average), averages based on astronomical measurements (such as a solar year being an average of 364.2422 days) or other approximations. In the cases where more than one definition is accepted for a unit, such as an eon, the most common definition was used on this chart.

This chart was somewhat inspired by the file "English Length Units Graph.svg."