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Converts a day of the year into a color hex value based on a supplied color mapping. For example, if Jan 01 is #FFF and Dec 31 is #000, then Jul 02 will work out to be a mid-grey (#808080).


var colorTime = require('color-time')({
    0: '#fff',
    365: '#000'
var feb1Color = colorTime('2015-02-01'); // #E9E9E9 
var rgbColorTime = require('color-time')({
    0: '#f00',
    182: '#0f0',
    365: '#00f'
var fallColor = rgbColorTime('Sep 4th, 2015', 'MMM Do, YYYY'); // #00A659 


Yearly Color Cycle

The module is a function used to create a function for retrieving the color for the specified date. Call the module function with the desired configuration of yearly colors to receive the curried value calculation function. The following example creates a calculation function using only a year-long red color:

var redColorTime = require('color-time')({
    0: '#f00'

To retrieve the value of a color for a given day, call that function with arguments that are parseable by moment.js.

var julyColor = redColorTime('Jul 1st, 2015', 'MMM Do, YYYY'); // #FF0000 
var decemberColor = redColorTime('2015-12-25'); // #FF0000 

Each numeric entry in the configuration hash corresponds to a 0-index day within the year, and can accept as many entries as needed. Note that the colors provided as the value of the hash must be in a format which color's constructor can use.

var randomColorTime = require('color-time')({
    0: '#f00',
    10: '#f9563f',
    20: '#dddaaa',
    30: '#009132',
    132: '#132132',
    256: '#aaa'

Color Aging

A color can be aged over time. To retrieve an aged color, first retrieve a calculation function with the desired aging properties. Required are maxAgeYears to describe over how many years a color may age to its maximum aged color, and maxAgeFilterPercentage to describe what percentage of the filter to apply at the maximum age.

An aging function must also be supplied. Currently built in filters, which get passed to the config as a string to agingFn, are:

  • 'greyscale' - Gradually shift the color to its greyscale value (converting color to greyscale)
  • fn(currentColorHexString, numberOfYearsToAge, maxAgeYears, maxAgeFilterPercentage) - Custom function to manually calculate an aged color

Example of a greyscale aging:

var agedColorTime = require('color-time')({
    0: '#f00',
    265: '#ff0',
    maxAgeYears: 10, // Age color to greyscale over 10 years 
    maxAgeFilterPercentage: .75, // At the end of the aging, the color has converted to 75% greyscale, 
    agingFn: 'greyscale'

A custom aging function may be provided to perform any desired modification to the color. It will be called with arguments from the config and from the calculation function: fn(currentColorHexString, numberOfYearsToAge, maxAgeYears, maxAgeFilterPercentage)

var agedColorTime = require('color-time')({
    0: '#f00',
    265: '#ff0',
    maxAgeYears: 10,
    maxAgeFilterPercentage: .75
    agingFn: function(currentColorHexString, numberOfYearsToAge, maxAgeYears, maxAgeFilterPercentage) {
        // Do whatever 
        return '#00f'; // Return a hex color string at the end 

To calculate a given color with an age, request the color as usual with a full date.

var agedColor = agedColorTime('Jul 1st, 1915', 'MMM Do, YYYY'); // Get the July 1st color, aged ~100 years 


  • <0-365> string|object Day of year as key, valid CSS color string or descriptive object (see color setters).
  • maxAgeYears number (optional, default: undefined) Maximum number of years a color can age for, after which no further aging modification will be added.
  • maxAgeFilterPercentage number (optional, default: undefined) A number between 0 and 1 indicating the maximum amount of the filter should be applied at the maximum age. 0 is no applied filter, 1 is filter added at 100% effect.
  • agingFn string|function (optional, default: noop) An optional function by which to calculate an aged color. May select from a built-in list of aging filters (see Color Aging) or provide a custom function (see above).