Time: Visualising time

Table of Contents

Introduction

We usually think of time as flowing linearly, so it seem natural to place events along a timeline, but this form of representaion is just 250 years old, with temporal information previously being recorded as annals and chronologies (Rosenberg and Grafton 2010). Categorical data located along a single temporal axis is a ‘timeline’ whereas a plot of quantitative data is a ‘time series’. Things also occilate or cycle though time driven by planetary movement and their own internal processes.

Annals and chronicals

Before the timeline temporal records were organised into ‘annals’ (event date lists) and narrated chronologies, with modern historical study emerging with modernity (idib.), to which may be added commercially and govenmental records.

Annals of St. Gall, Switzerland began in 709 (Codex Sangallensis 915, Public domain, via Wikimedia Commons).

Information in such records is often scant and contradictory, for example Goodchild (2007) identified just four reported cereal yeilds ranging from 8:1 to 100:1 for The Middle Tiber Valley, Italy, during the Roman period.

Timeline

A timeline locates point and duration events along a temporal line.

Points in time. Stylized evolution of the academic degrowth discourse (Fig. 5 in Weiss and Cattaneo 2017).

Durations in time. Ancient Greek philosophers’ timelines (reproduced from *Democritus*, by Paul Cartledge, publ by Phoenix, 1998 via OrnaVerum)

Long timelines require a long page or may be wrapped across a page to fit.

A Timeline of Major Western Philosophers. (Suits, 2008. Published on Rochester Institute of Technology website).

‘Wrapped’ time line. History of the Department of Statistics, Oxford University (Oxford University).

Spiralling proves an alternative means of fitting a long timeline in a restricted space. Here, ‘deep’ geological time has been log-scaled and displayed as a spiral. The log scale works because we have less information about the past. Spiral thickess increases with information growth though time.

The geologic time scale, proportionally represented as a log-spiral with some major events in Earth’s history (Jarred C Lloyd, CC BY 4.0 https://creativecommons.org/licenses/by/4.0, via Wikimedia Commons).

Timelines may also be linked into ‘streams’ or ‘rivers’.

Sebastian Adams’ 1881 Synchronological Chart of Universal History is 23 feet long and shows 5,885 years of history, from 4004 B.C. to 1881 A.D. (David Rumsey Maps).

A genealogy is a reticlate timeline network.

‘My take on a British Royal Family Tree Chart’. Click link to access orginal full scale version (BlankCanvas609, r/UsefulCharts).

Time series

Time series plot quantitative values against a temporal axis with records. The global average temprature record over the last 540 million years shows the types of pattern that time series may contain, including peaks, toughs, isolated spikes, trends and oscillations (cycles), and how climate change involves both trends and cycles. It is a composite time series synthesised from a range of data sources in which temporal resolution decreases with age. The ‘Climategate’ controversy is a salient reminder of the importance of openess and considered language when synthesising temporal or other data from multiple sources.

Global average temperature estimates for the last 540 My (Glen Fergus, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons).

Time series plotted on the same axis facilitate comparison, however readability declines as the greater number of time series and overlap increase. Plotting eleven supermarket time-series on a single plot just about works as series overlap is not high, but some of the series in the low group are difficult to trace, particularly Lidl.

Plotting as stacked an area graph visually seperates series, but the y-axis is scaled to the maximum sum of all values, which reduces vertical variation within series and prevents the simple reading of the value for a store in a year. In this case, the loss of vertical variation significantly impacts the utlity of the plot.

Multiple time-series area plot. Total store area m2 of the UK’s eleven largest supermarket chains (SupMrktComp, Kidd 2025).

Contast the total store area to the plot of new store area in which series vary within a similar range and cross more frequently. In this case an area-plot is more approriate.

Multiple time-series line plot. New store area m2 of the UK’s eleven largest supermarket chains (SupMrktComp, Kidd 2025).

Multiple time-series area plot. New store area m2 of the UK’s eleven largest supermarket chains (SupMrktComp, Kidd 2025).

Line and area plots reveal cyclic/occilatory behaviour as periodic rise and fall in value. Occilations may be extrenally directly or indirectly driven by variation in energy reaching the earth resulting from its tilt, and rotation around its axis (daily cycle) and the sun (annual cycle), as well as longer Milankovitch cycles that stem from orbital eccentricites.

Daily temperature in an urban heat island (Part of Fig 3 in Jiang et al. 2009).

Past and future Milankovitch cycles via VSOP model Graphic shows variations in five orbital elements: Axial tilt or obliquity (ε). Eccentricity (e). Longitude of perihelion (sin(ϖ)). Precession index (e sin(ϖ)) Precession index and obliquity control insolation at each latitude: Daily-average insolation at top of atmosphere on summer solstice at 65° N Ocean sediment and Antarctic ice strata record ancient sea levels and temperatures: Benthic forams (57 widespread locations) Vostok ice core (Antarctica) Vertical gray line shows present (2000 CE) (Incredio, CC BY 3.0 https://creativecommons.org/licenses/by/3.0, via Wikimedia Commons).

Cycles may also result from the internal working of earth and biological systems, for example, the El Niño-Southern Oscillation and predator-prey interactions. Phenomena may be subject to more than one cyclic driver; for example, a predator-prey cycle may be modulated by the El Niño-Southern Oscillation.

ENSO warm and cold phases and observational record. a Examples of strong El Niño (top) and La Niña (bottom) events seen in the tropical Pacific surface temperature (SST) distribution, with characteristic strong and weak SST gradient along the equator, respectively. b ENSO record since the 1980s. Note the three extreme events of the past four decades (1982, 1997 and 2015) and the weakening of ENSO variability between years 2000 and 2015. Temperature is averaged for the NINO3 region (5ºC-5ºN, 150ºW-90ºW) in the eastern equatorial Pacific. Based on NOAA Extended Reconstructed SST V5 data (Huang et al., 2017 in Lenton et. al 2023).

8-11 year Hare-Lynx preditor prey cycle (University of Alberta Lynx Project via Edmonton & Area Land Trust).

A dated evolutionary tree might be thought of as a hierarchical timeline, as ‘diversification’ is a qualitative event that divides an ancestor into isolated descendants. Nodes and branches, however, are often symbolized to show quantitative values, making it both a timeline and a series network. Here a tree is displayed radially with the time increasing from the common ancestor in the center to living taxa around the circle.

Bayesian ancestral state reconstruction of substrate preference in mammals with pie charts of posterior probability (Fig 1 in Hughes et al 2001, via ResearchGate).

The display of both qualitative and quantitative data against the same timeline is not unusual, so the distinction between lines and series is false; nevertheless, most linear temporal visualization may be assigned to one of these categories.

Radial time

Radial plots show patterns within a cycle or average patterns across cycles, for example, the number of road accidents each hour in a day.

Radial plot of frequency of accidents by hour (Seattle Government via storytellingwithdata.com).

Polar seasonal plot of monthly antidiabetic drug sales in Australia (Fig 2.5 in Hyndman and Athanasopoulos 2018).

The NASA climate spiral visualization animation show increasing global warming through time as a radial plot, before changing viewpoint to reveal it is actually 3D time-spiral.

The NASA climate spiral visualization. (Hawkins and SubbaRao 2023/Lenssen et al. 2024 via YouTube, MechDesignTV)

<<< Aspects of time

Visualising space and time >>>

References

Goodchild, H. (2007). Modelling Roman Agricultural Production in the Middle Tiber Valley, Central Italy. PhD Thesis, Institute of Archaeology and Antiquity School of Historical Studies, The University of Birmingham. https://etheses.bham.ac.uk/id/eprint/175/1/Goodchild07PhD.pdf

Rosenberg, G. and Grafton, A. (2010). Cartographies of Time. Princeton Architectural Press, New York.