Three issues in mapping Time to a line

I have just submitted an article to a design journal. It is concerned with just one topic: the mapping of time to a line. It is a plea for designers and others to take more seriously the following issues:

1. If time is mapped to a line, on which axis of the graphic surface should it lie? And in which direction should later times lie in relation to earlier: what is the direction of travel? Is there a solution to these questions that is the most natural, the best - or simply right?
2. How does time map to dimension; what model of time does such mapping presuppose? There is an indefinite number of possible mappings but, in practice, the principal options tend to be (1) strict linearity where equal space stands for equal time, (2) mathematically consistent non-linearity such as a logarithmic scale, usually giving more space to most recent time, (3) scaling which divides time into periods, each of which is linear but where the more recent periods are on a larger scale than those more distant. There are also examples of a more pragmatic approach, where the space allotted is adjusted to accommodate the density of events.
3. Calibration. There are several reasons why different measures of time may be needed. One is to reflect the varied cultures of the users (see figure). Within a single culture there may be rival dating schemes because of differing scholarly opinion. And it may simply be useful to have more than one calibration of a chart, for example dates counted forwards from a point in history to our own time as well as dates counted backwards from the present day.

A bronze cannon cast in France in March/April 1795AD. Rather than using 'our' Gregorian calendar, it bears the French Republican date: month Germinal in Revolutionary Year 3. Neither at present, nor in history, is the Gregorian the only calendar. Photographed at St Michael’s Mount, Cornwall, UK, 2008. Photo: Stephen Boyd Davis.

As usual, I argue in the article that current thinking and practice is pretty rudimentary compared with the sophistication of early chronographers in the eighteenth century. Working through evidence that there are no right answers to the questions above, I propose some principles for approaching the questions and offer a research agenda.

If the article is published, it should come out some time next year. I'll put a few snippets from it here in the coming months, including a discussion of Nicole Oresme (c. 1320-5 - July 11, 1382) who may have been the first to draw time as a line.

Link: Wikipedia article on the French Republican Calendar (which also tells you what today's date is in that calendar).