Not Particularly Meaningful


    2.0.0 • Public • Published


    Convert between RFC2445 RRULE and its JSON equivalent AND see the future (and past). Useful with rrule.js.

    If you want UIs like these:

    Google Calendar:

    Thunderbird Calendar:

    Kendo Calendar:

    You need a schedule-logic library like this to actually interpret RRULEs and schedule the events.


    parse & stringify

    This snippet will work both in the Browser and with Node.js (hence the scary bit at the bottom).

    From JSON to RRULE

    (function (exports) {
      'use strict';
      var Rrecur = exports.Rrecur || require('rrecur').Rrecur
        , rfcString
      // every other month on the first and last sunday
      rfcString = Rrecur.stringify({
        "freq": "monthly"
      , "interval": "2"
      , "count": "10"
      , "byday": ["1su","-1su"]
    }('undefined' !== typeof exports && exports || new Function('return this')()));

    From RRULE to JSON

    (function (exports) {
      'use strict';
      var Rrecur = exports.Rrecur || require('rrecur').Rrecur
        , rfcString
        , rruleObject
      rruleObject = Rrecur.parse(rfcString);
      // Also supports sans-RRULE prefix plus DTSTART for the sake of `rrule.js` compatability
      rfcString = "DTSTART=20140616T103000Z;FREQ=DAILY;BYHOUR=10;BYMINUTE=30;BYSECOND=0;UNTIL=20150616T153000Z";
      rruleObject = Rrecur.parse(rfcString);
    }('undefined' !== typeof exports && exports || new Function('return this')()));

    next occurrence of an event

    Scenario: I want an alarm to go off every day at 10:30am, given my location.

    Since we can't specify timezones with a JavaScript date object, we pretend internally that local time is zoneless time. UTC is handled exactly as UTC.

    So let's say it's 8:00am on our server in Utah on the first day of summer and we want to set an alarm for 10:30am in New York (30 minutes from now) every mon, wed, fri:

    var rrecur
    rrecur = Rrecur.create({
      dtstart: {
        zoneless: Rrecur.toLocaleISOString(new Date(2014,06,21, 10,30,0), "GMT-0400 (EDT)")
        // OR utc: new Date(2014,06,21, 10,30,0).toISOString()
      , locale: "GMT-0400 (EDT)"
    , rrule: {
        freq: 'daily'
      , until: Rrecur.toAdjustedISOString(new Date(2014,06,22, 10,30,0), "GMT-0400 (EDT)")
      , count: 1
      , byhour: [10]
      , byminute: [30]
      , byday: ['mo','we','fr'] // Or [Rrecur.weekdays[1], Rrecur.weekdays[3], Rrecur.weekdays[5]]
      // `bysecond` will default to 00, since that's what's specified in `dtstart`
    }, new Date());
; // 2014-05-21T10:30:00.000-0400

    If you didn't specify locale then you would get back a time in UTC or in GMT-0600 (MDT) that you would need to manually adjust.

    Whether you specify zoneless or utc, you must still specify locale.

    one-time events

    var rrecur
    rrecur = Rrecur.create({
      dtstart: {
        locale: new Date(2014,06,21, 10,30,0).toString()
    , rrule: null
    }, new Date());
    // Assuming you specified the Date on a machine running on MDT; // 2014-07-21T16:30:00.000-0000

    For one-time events you may simply use a locale string, which will be converted into to both zoneless and utc for internal purposes.

    Also, rrule will be automatically populated to match the zoneless dtstart.



    NOTE: you only need rrecur.js for the basic JSON <-> RRULE conversion. If you want to actually find the occurances you'll need underscore.js, rrule.js, and moment.js, and rrecur-iterator.js. However, in some future version I may be able to eliminate underscore.js and rrule.js.

    via bower

    bower install rrecur

    via download


    and insert the script tag, of course

    <script src="underscore.js"></script>
    <script src="rrule.js"></script>
    <script src="moment.js"></script>
    <script src="rrecur.js"></script>
    <script src="rrecur-iterator.js"></script>

    I know, it's a lot of dependencies... but that's just how it is. In a future version it may be reasonable to drop underscore and rrule (or at least substitute lodash for underscore), but moment is a must. JavaScript's Date object is just too messed up.


    npm install rrecur


    Convert between RFC2445 RRULE and its JSON equivalent.

    • Rrecur.parse(rruleStr) - parses a string rrule (allows non-standard dtstart in string)
    • Rrecur.stringify(rruleObj) - stringifies an rrule object (allows non-standard dtstart)

    Find the next (or previous) occurence of an event in an rrule chain.

    • Rrecur.create(rrule, localeDateString) - creates a wrapped instance from rrule.js from an rrule object or string
      • localeDateString - a string such as Wed Jul 16 2014 10:30:00 GMT-0400 (EDT)
      • Rrecur#previous() - cycles backwards through time to find a previous instance up to dtstart
      • Rrecur#next() - cycles forwards through time to find the next instance up to until or count

    Utility functions

    • Rrecur.toLocaleISOString(date, [locale]) - ouput an ISO string with timezone information
      • 2014-06-21T10:00:00.000-0600 instead of Sat Jun 21 2014 10:15:08 GMT-0600 (MDT) or 2014-06-21T16:00:00.000Z
      • If locale is specified in a format such as -04:00 or GMT-0400 (EDT), the local (not UTC) time is still used, but the offset is replaced with the supplied locale.
    • Rrecur.toAdjustedISOString(date, locale)
      • date - A local date object (with the wrong timezone)
      • locale A JavaScript Locale string (or Date string) with the desired timezone
      • returns a UTC string adjusted to accurately represent the desired timezone


    You put in an object like this:

    { "freq": "weekly"
    , "until": "2015-01-01T10:30:00.000Z"
    , "byday": ["tu", "th"]
    , "byhour": [4]
    , "byminute": [30]
    • freq - yearly|monthly|weekly|daily|hourly|minutely|secondly
    • interval - bi-weekly, tri-weekly, etc
    • bymonth
    • byweekno
    • byyearday
    • bymonthday
    • byday - 0-7, su,mo,tu,we,th,fr,sa,su
    • byhour
    • byminute
    • bysecond
    • until - seems that this must be given in UTC as per spec, which is weird
    • count - how many occurrences
    • wkst - which day the week starts on 0-7, sa,su,mo
    • bysetpos - not sure how this works -
    • dtstart - specifies the first event (or a date close to it), non-standard as part of rrule, but is part of ical
      • If you don't specify dtstart, the current time will be used.
      • You cannot get previous() before dtstart
    • locale - specifies the locale in the format GMT-0500 (EST) - non-standard, in general
    • tzid - specifies the locale, non-standard as part of rrule, but is part of ical

    See for implementation details.


    JSON version of iCal RRULE

    { "freq": "daily"
    , "until": "2015-01-01T10:30:00.000Z"
    , "byday": ["tu", "th"]
    , "byhour": [4]
    , "byminute": [30]

    Non-standard iCal directive

    (once TZID is implemented, this will be standard)

    DTSTART;LOCALE=GMT-0500 (EST):20140616T103000

    Non-standard iCal directive (rrule.js-flavored)



    Because I needed a place to rant.


    Timezones are a PAIN! Right!?

    We take care of the hard brainwork for you, but just so you know:

    Here are the problems:

    • JavaScript's native Date object has only two options - Locale and UTC
    • The server may have a different locale than the client
    • rrule.js only operates on Locale - the local time of the server
    • RRULEs are zoneless - 10:30am is meant to be in the user's time
    • DTSTART;TZID=America/New_York isn't yet supported by rrule.js

    Here are solutions:

    • DTSTART you can include LOCALE (recommended) or use UTC (confusing)
    • UNTIL you must use UTC (confusing, but that's the way it is)
      • Try Rrecur.toAdjustedISOString(new Date(2014,06,16,10,30,00), 'GMT-0600 (MDT)')
    • RRULEs are zoneless, but we do our best to put them in the right zone.
    • Everything is calculated in local time under the hood.


    • Always specify RRULEs in local time (except DTSTART and UNTIL in UTC).
      • An RRULE for Monday at 10am will fire well after the sun is risen whether in California or China
      • An RRULE for Monday at 10am will have a different UTC conversion in California than in China
      • dtstart should always be in UTC or in local time with a locale
      • until must be specified in UTC
      • all calculations will be done in the local time of the server


    npm i rrecur

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