A natural language date parser in Javascript

npm install chrono-node
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A natural language date parser in Javascript. It is designed to extract date informations from any given text.

Chrono supports a number of date and time formats, including :

  • Today, Tomorrow, Yesterday, last Friday, etc
  • 10/13/2013
  • this Friday from 13:00 - 16.00
  • Saturday, 17 August 2013 - Monday, 19 August 2013
  • Sat Aug 17 2013 18:40:39 GMT+0900 (JST)


npm install chrono-node


<script src=""></script>


Just pass a string to function chrono.parseDate or chrono.parse.

> var chrono = require('chrono-node')

> chrono.parseDate('An appointment on Sep 12-13') 
Thu Sep 12 2013 12:00:00 GMT+0900 (JST)

> chrono.parse('An appointment on Sep 12-13')    
[ { start: 
     { year: 2013,
       month: 8,
       day: 12,
       impliedComponents: [Object],
       isCertain: [Function],
       date: [Function] },
    startDate: Thu Sep 12 2013 12:00:00 GMT+0900 (JST),
     { year: 2013,
       month: 8,
       day: 13,
       impliedComponents: [Object],
       isCertain: [Function],
       date: [Function] },
    endDate: Fri Sep 13 2013 12:00:00 GMT+0900 (JST),
    referenceDate: Sat Aug 17 2013 17:54:57 GMT+0900 (JST),
    index: 18,
    text: 'Sep 12-13',
    concordance: 'An appointment on Sep 12-13' } ]

Reference Date

Today's "Friday" is difference from last month's "Friday". The meaning of mentioned dates are depended on when they were mentioned. Chrono let you define the reference date using chrono.parse(text,ref) and chrono.parseDate(text,ref).

> chrono.parseDate('Friday', new Date(2012,7,23)); 
Fri Aug 24 2012 12:00:00 GMT+0700 (ICT)

> chrono.parseDate('Friday', new Date(2012,7,1)); 
Fri Aug 03 2012 12:00:00 GMT+0700 (ICT)


Chrono is designed to work with long text (notes, emails, articles, etc). chrono.parse will return an array of every date mentioned in the story.

> var text = 'October 7, 2011, of which details were not revealed out of respect to Jobs\'s family.[239] Apple announced on the same day that they had no plans for a public service, but were encouraging "well-wishers" to send their remembrance messages to an email address created to receive such messages.[240] Sunday, October 16, 2011'
> chrono.parse(text)
[{ start: 
    { year: 2011,
      month: 9,
      day: 7,
 { start: 
    { year: 2011,
      month: 9,
      day: 16,

Parsing Result

Chrono provides very detailed parsing results as objects of class chrono.ParseResult.

  • start (chrono.DateComponents) : The parsing result as a DateComponents object
  • startDate (Date) : The parsing result as a javascript Date object
  • end (chrono.DateComponents) endDate (Date) : Similar to start and startDate (Optional)
  • index (int) : The location within the input text of this result
  • text (string) : The mentioned words within the input text of this result
  • concordance (string) : The context of mentioned words within the input text (up to 30 characters)
  • referenceDate (Date) : The reference date of this result

Date Components

  • year,month,day, dayOfWeek, hour, minute, second : The datected components
  • impliedComponents (array) : The components that are not explicitly mentioned
  • date ( function ) : Return a javascript Date

Customize Chrono


Parser is a module for low-level parsing. Each parser is designed to handle a single specific date format. In Chrono's parsing process, a number of parsers will be used togather to produce the results. You should define new type of parsers for supporting new date formats or languages.

Chrono create parser objects by factory method pattern. To add a new type of parser, declare a new factory function in chrono.parsers. Within that function:

  • Create an object from chrono.Parser()
  • Override the object's pattern and extract methods
  • Return the object
chrono.parsers.ChrismasParser = function(text, ref, opt) {

  // Create a chrono's base parser
  var parser = chrono.Parser(text, ref, opt); 

  // Extend the parser with our pattern
  parser.pattern = function () { return /Christmas/i } // Provide search pattern
  parser.extract = function(text, index) { 
    // Chrono will find all indexes of the text that match our pattern.
    // We need to check and return the result 
    var mentioned_text = text.substr(index).match(/Christmas/i)[0];
    return new chrono.ParseResult({
      referenceDate : ref,
      text : mentioned_text,
      index: index,
      start: {
        day: 25, month: 11, // It's 25 December
        year: ref.getFullYear() // But we don't sure about the 'year' 
        impliedComponents: ['year'] 

  return parser;


// Lets chrono merge and refine our result (See. '2.30 AM')
> chrono.parseDate("I'll arrive at 2.30AM on Christmas night")
Wed Dec 25 2013 02:30:00 GMT+0900 (JST)
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