Right Twice a Day

Exercise 1: Mapping Time


Gather all the necessary software and files to get started:

The P5.js site has an extensive Reference section with a full listing of the drawing commands that make up its API. It’s also got a somewhat sparser set of Tutorials that might help you get started (but mostly seem to be written to an audience that’s familiar with the original Processing environment so YMMV).

For this assignment, make sure you’ve got a handle on these basics:

To get yourself situated, try looking over the sample code in the examples directory. Note the basic form of each of the programs (i.e., their setup() and draw() definitions), how they employ the drawing commands listed above, and particularly their use of variables to hold partial computations and for-loops to encapsulate repeated procedures.


For this project the ‘data’ you'll be working with are the numerical aspects of time. You should familiarize yourself with the clock() function I've provided to help access the current date & time. The function returns a time Object with the current instant broken down into individual components. You can get numerical values for hour, min, sec, and ms on the time side of things and year, season, month, moon, day, and weekday if you’re interested in dates.

For instance, you can use the current year to work backwards:

var now = clock(),
    age = 64,
    born = now.year - age;
print(`A ${age}-year-old would have been born in ${born}`)

To determine what half of the day it currently is, access the am and pm attributes, each of which contains a Boolean. You could conceivably use this to set the background color depending on whether it’s before- or afternoon.

function draw(){
  var now = clock()
  if (now.pm){

The object returned by clock() also provides a mechanism for measuring the current time in terms of the cyclic features of the calendar. By accessing fields of its progress attribute, you can get the fraction of various periods that have elapsed before the current moment. The clock represents progress as a number between 0 and 1 for each of: year, season, moon, month, week, day, halfday, hour, min, and sec.

For instance, if you wanted to be fairly literal and draw a progress bar for the day, try drawing a black rectangle whose width is proportional to the ‘doneness’ of the current 24-hour cycle:

function draw(){

  var now = clock(),
      pct = now.progress.day;
  rect(0,0, width*pct, height)


  • Create a visual representation of the current local time using only graphics primitives, symbols, and formal elements like color/texture/size — no text or alphanumeric characters!
  • Use the clock() function so that your sketch is always displaying the current time in your draw() function.
  • This is to be a creative interpretation of the idea of a clock. Your focus should be on inventiveness and polished visuals.
  • Your interpretation needs to be legible to you (the author), and you need to be able to explain how the time is derived visually at any given point.
  • Your clock concept needs a name (put that in the <title> tag of the index.html file).
  • For the extra-ambitious:
    • Rather than just plotting the current time as a static quantity, plot the relative amount of time between 2 or more ‘events’ in a given day. Consider tracking your own behavior or the occurrence of a repeating event in the world and depicting when it happens – relative either to the time-of-day or to other occurrences.
    • Calendar time is much more complicated than ‘wall clock’ time. But you can attempt to visualize days, weeks, months, seasons, years, etc. using the date-related fields in the progress attribute ... if you dare.
    • The clock() function uses the Moment.js library behind the scenes for its calculations. You can access the moment attribute of the time object if you want to do anything more sophisticated than what clock() is already unpacking.


  • Make sure you only create or modify files within the students/ampm/<your-name> subdirectory.
  • Start off by making some hand-drawn (or mocked up in a drawing app) sketches of clock ideas and put these images into the process folder of your subdirectory.
  • Update the README.md file in your process folder describing what’s in your various sketch files, the logic of the representation, etc. Be sure to explain, either in words or diagrammatically, your chosen mapping of time components to Bertin-ian Retinal Variables.
  • Commit your changes whenever you’ve made some modifications that feel like they’re in a stable state (or if you stumble onto a glitchy visual that points in a direction you’d like to explore). This will let you ‘rewind’ to that point in the future if you’ve hit a dead-end or need to remember how you did something.
  • When you make a commit, select just the files (or even just the lines within one) that are part of the ‘conceptual unit’ of change that you made and type a brief description of what changed into the Summary field.
  • Sync your local repository with the copy on GitHub before the start of class next week.
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