rrecur

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: http://imgur.com/a/gT7Af

Thunderbird Calendar: http://imgur.com/a/LhnWU

Kendo Calendar: http://imgur.com/a/zVLyg

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

Usage

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
    ;
 
  rfcString = "RRULE:FREQ=MONTHLY;INTERVAL=2;COUNT=10;BYDAY=1SU,-1SU";
  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());
 
rrecur.next(); // 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
rrecur.next(); // 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.

Installation

browser

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

wget https://raw2.github.com/coolaj86/rrecurjs/master/rrecur.js
wget https://raw2.github.com/coolaj86/rrecurjs/master/rrecur-iterator.js

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>

script(src="underscore.js")
script(src="rrule.js")
script(src="moment.js")
script(src="rrecur.js")
script(src="rrecur-iterator.js")

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.

node.js

npm install rrecur

API

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

RRULEs

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 - http://www.kanzaki.com/docs/ical/recur.html
• 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 https://github.com/jkbr/rrule#api for implementation details.

Examples

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
RRULE:FREQ=DAILY;BYHOUR=10;BYMINUTE=30;BYSECOND=0;UNTIL=20150616T153000Z

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

DTSTART=20140616T103000Z;FREQ=DAILY;BYHOUR=10;BYMINUTE=30;BYSECOND=0;UNTIL=20150616T153000Z

Appendix

Because I needed a place to rant.

Timezones

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.

Remember:

• 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