Library for working with recurrence rules for calendar dates.

rrule.js supports recurrence rules as defined in the iCalendar RFC, with a few important differences. It is a partial port of the rrule module from the excellent python-dateutil library. On top of that, it supports parsing and serialization of recurrence rules from and to natural language.

• Demo app

• For contributors and maintainers: the code for the demo app is only on gh-pages branch

$ yarn add rrule

Includes optional TypeScript types

$ yarn add rrule
# or
$ npm install rrule

RRule:

import { datetime, RRule, RRuleSet, rrulestr } from 'rrule'

// Create a rule:
const rule = new RRule({
  freq: RRule.WEEKLY,
  interval: 5,
  byweekday: [RRule.MO, RRule.FR],
  dtstart: datetime(2012, 2, 1, 10, 30),
  until: datetime(2012, 12, 31)
})

// Get all occurrence dates (Date instances):
rule.all()
[ '2012-02-03T10:30:00.000Z',
  '2012-03-05T10:30:00.000Z',
  '2012-03-09T10:30:00.000Z',
  '2012-04-09T10:30:00.000Z',
  '2012-04-13T10:30:00.000Z',
  '2012-05-14T10:30:00.000Z',
  '2012-05-18T10:30:00.000Z',

 /* … */]

// Get a slice:
rule.between(datetime(2012, 8, 1), datetime(2012, 9, 1))
['2012-08-27T10:30:00.000Z',
 '2012-08-31T10:30:00.000Z']

// Get an iCalendar RRULE string representation:
// The output can be used with RRule.fromString().
rule.toString()
"DTSTART:20120201T093000Z\nRRULE:FREQ=WEEKLY;INTERVAL=5;UNTIL=20130130T230000Z;BYDAY=MO,FR"

// Get a human-friendly text representation:
// The output can be used with RRule.fromText().
rule.toText()
"every 5 weeks on Monday, Friday until January 31, 2013"

RRuleSet:

const rruleSet = new RRuleSet()

// Add a rrule to rruleSet
rruleSet.rrule(
  new RRule({
    freq: RRule.MONTHLY,
    count: 5,
    dtstart: datetime(2012, 2, 1, 10, 30),
  })
)

// Add a date to rruleSet
rruleSet.rdate(datetime(2012, 7, 1, 10, 30))

// Add another date to rruleSet
rruleSet.rdate(datetime(2012, 7, 2, 10, 30))

// Add a exclusion rrule to rruleSet
rruleSet.exrule(
  new RRule({
    freq: RRule.MONTHLY,
    count: 2,
    dtstart: datetime(2012, 3, 1, 10, 30),
  })
)

// Add a exclusion date to rruleSet
rruleSet.exdate(datetime(2012, 5, 1, 10, 30))

// Get all occurrence dates (Date instances):
rruleSet.all()[
  ('2012-02-01T10:30:00.000Z',
  '2012-05-01T10:30:00.000Z',
  '2012-07-01T10:30:00.000Z',
  '2012-07-02T10:30:00.000Z')
]

// Get a slice:
rruleSet.between(datetime(2012, 2, 1), datetime(2012, 6, 2))[
  ('2012-05-01T10:30:00.000Z', '2012-07-01T10:30:00.000Z')
]

// To string
rruleSet.valueOf()[
  ('DTSTART:20120201T023000Z',
  'RRULE:FREQ=MONTHLY;COUNT=5',
  'RDATE:20120701T023000Z,20120702T023000Z',
  'EXRULE:FREQ=MONTHLY;COUNT=2',
  'EXDATE:20120601T023000Z')
]

// To string
rruleSet.toString()
;('["DTSTART:20120201T023000Z","RRULE:FREQ=MONTHLY;COUNT=5","RDATE:20120701T023000Z,20120702T023000Z","EXRULE:FREQ=MONTHLY;COUNT=2","EXDATE:20120601T023000Z"]')

rrulestr:

// Parse a RRule string, return a RRule object
rrulestr('DTSTART:20120201T023000Z\nRRULE:FREQ=MONTHLY;COUNT=5')

// Parse a RRule string, return a RRuleSet object
rrulestr('DTSTART:20120201T023000Z\nRRULE:FREQ=MONTHLY;COUNT=5', {
  forceset: true,
})

// Parse a RRuleSet string, return a RRuleSet object
rrulestr(
  'DTSTART:20120201T023000Z\nRRULE:FREQ=MONTHLY;COUNT=5\nRDATE:20120701T023000Z,20120702T023000Z\nEXRULE:FREQ=MONTHLY;COUNT=2\nEXDATE:20120601T023000Z'
)

Dates in JavaScript are tricky. RRule tries to support as much flexibility as possible without adding any large required 3rd party dependencies, but that means we also have some special rules.

By default, RRule deals in "floating" times or UTC timezones. If you want results in a specific timezone, RRule also provides timezone support. Either way, JavaScript's built-in "timezone" offset tends to just get in the way, so this library simply doesn't use it at all. All times are returned with zero offset, as though it didn't exist in JavaScript.

THE BOTTOM LINE: Returned "UTC" dates are always meant to be interpreted as dates in your local timezone. This may mean you have to do additional conversion to get the "correct" local time with offset applied.

For this reason, it is highly recommended to use timestamps in UTC eg. new Date(Date.UTC(...)). Returned dates will likewise be in UTC (except on Chrome, which always returns dates with a timezone offset). It's recommended to use the provided datetime() helper, which creates dates in the correct format using a 1-based month.

For example:

// local machine zone is America/Los_Angeles
const rule = RRule.fromString(
  "DTSTART;TZID=America/Denver:20181101T195000;\n"
    "RRULE:FREQ=WEEKLY;BYDAY=MO,WE,TH;INTERVAL=1;COUNT=3"
)
rule.all()

[ 2018-11-01T18:00:00.000Z,
  2018-11-05T18:00:00.000Z,
  2018-11-07T18:00:00.000Z ]
// Even though the given offset is `Z` (UTC), these are local times, not UTC times.
// Each of these this is the correct local Pacific time of each recurrence in
// America/Los_Angeles when it is 19:00 in America/Denver, including the DST shift.

// You can get the local components by using the getUTC* methods eg:
date.getUTCDate() // --> 1
date.getUTCHours() // --> 18

If you want to get the same times in true UTC, you may do so (e.g., using Luxon):

rule.all().map(date =>
DateTime.fromJSDate(date)
  .toUTC()
  .setZone('local', { keepLocalTime: true })
  .toJSDate()
)

[ 2018-11-02T01:00:00.000Z,
  2018-11-06T02:00:00.000Z,
  2018-11-08T02:00:00.000Z ]
// These times are in true UTC; you can see the hours shift

For more examples see python-dateutil documentation.

Rrule also supports use of the TZID parameter in the RFC using the Intl API. Support matrix for the Intl API applies. If you need to support additional environments, please consider using a polyfill.

Example with TZID:

new RRule({
  dtstart: datetime(2018, 2, 1, 10, 30),
  count: 1,
  tzid: 'Asia/Tokyo',
}).all()[
  // assuming the system timezone is set to America/Los_Angeles, you get:
  '2018-01-31T17:30:00.000Z'
]
// which is the time in Los Angeles when it's 2018-02-01T10:30:00 in Tokyo.

Whether or not you use the TZID param, make sure to only use JS Date objects that are represented in UTC to avoid unexpected timezone offsets being applied, for example:

// WRONG: Will produce dates with TZ offsets added
new RRule({
  freq: RRule.MONTHLY,
  dtstart: new Date(2018, 1, 1, 10, 30),
  until: new Date(2018, 2, 31),
}).all()[('2018-02-01T18:30:00.000Z', '2018-03-01T18:30:00.000Z')]

// RIGHT: Will produce dates with recurrences at the correct time
new RRule({
  freq: RRule.MONTHLY,
  dtstart: datetime(2018, 2, 1, 10, 30),
  until: datetime(2018, 3, 31),
}).all()[('2018-02-01T10:30:00.000Z', '2018-03-01T10:30:00.000Z')]

new RRule(options[, noCache=false])

The options argument mostly corresponds to the properties defined for RRULE in the iCalendar RFC. Only freq is required.

noCache: Set to true to disable caching of results. If you will use the same rrule instance multiple times, enabling caching will improve the performance considerably. Enabled by default.

See also python-dateutil documentation.

rule.options

Processed options applied to the rule. Includes default options (such us wkstart). Currently, rule.options.byweekday isn't equal to rule.origOptions.byweekday (which is an inconsistency).

rule.origOptions

The original options argument passed to the constructor.

Returns all dates matching the rule. It is a replacement for the iterator protocol this class implements in the Python version.

As rules without until or count represent infinite date series, you can optionally pass iterator, which is a function that is called for each date matched by the rule. It gets two parameters date (the Date instance being added), and i (zero-indexed position of date in the result). Dates are being added to the result as long as the iterator returns true. If a false-y value is returned, date isn't added to the result and the iteration is interrupted (possibly prematurely).

rule.all()[
  ('2012-02-01T10:30:00.000Z',
  '2012-05-01T10:30:00.000Z',
  '2012-07-01T10:30:00.000Z',
  '2012-07-02T10:30:00.000Z')
]

rule.all(function (date, i) {
  return i < 2
})[('2012-02-01T10:30:00.000Z', '2012-05-01T10:30:00.000Z')]

Returns all the occurrences of the rrule between after and before. The inc keyword defines what happens if after and/or before are themselves occurrences. With inc == true, they will be included in the list, if they are found in the recurrence set.

Optional iterator has the same function as it has with RRule.prototype.all().

rule.between(datetime(2012, 8, 1), datetime(2012, 9, 1))[
  ('2012-08-27T10:30:00.000Z', '2012-08-31T10:30:00.000Z')
]

Returns the last recurrence before the given Date instance. The inc argument defines what happens if dt is an occurrence. With inc == true, if dt itself is an occurrence, it will be returned.

Returns the first recurrence after the given Date instance. The inc argument defines what happens if dt is an occurrence. With inc == true, if dt itself is an occurrence, it will be returned.

See also python-dateutil documentation.

Returns a string representation of the rule as per the iCalendar RFC. Only properties explicitly specified in options are included:

rule.toString()
;('DTSTART:20120201T093000Z\nRRULE:FREQ=WEEKLY;INTERVAL=5;UNTIL=20130130T230000Z;BYDAY=MO,FR')

rule.toString() == RRule.optionsToString(rule.origOptions)
true

Converts options to iCalendar RFC RRULE string:

// Get full a string representation of all options,
// including the default and inferred ones.
RRule.optionsToString(rule.options)
;('DTSTART:20120201T093000Z\nRRULE:FREQ=WEEKLY;INTERVAL=5;WKST=0;UNTIL=20130130T230000Z;BYDAY=MO,FR;BYHOUR=10;BYMINUTE=30;BYSECOND=0')

// Cherry-pick only some options from an rrule:
RRule.optionsToString({
  freq: rule.options.freq,
  dtstart: rule.options.dtstart,
})
;('DTSTART:20120201T093000Z\nRRULE:FREQ=WEEKLY;')

Constructs an RRule instance from a complete rfcString:

var rule = RRule.fromString('DTSTART:20120201T093000Z\nRRULE:FREQ=WEEKLY;')

// This is equivalent
var rule = new RRule(
  RRule.parseString('DTSTART:20120201T093000Z\nRRULE:FREQ=WEEKLY')
)

Only parse RFC string and return options.

var options = RRule.parseString('FREQ=DAILY;INTERVAL=6')
options.dtstart = datetime(2000, 2, 1)
var rule = new RRule(options)

These methods provide an incomplete support for text→RRule and RRule→text conversion. You should test them with your input to see whether the result is acceptable.

Returns a textual representation of rule. The gettext callback, if provided, will be called for each text token and its return value used instead. The optional language argument is a language definition to be used (defaults to rrule/nlp.js:ENGLISH).

var rule = new RRule({
  freq: RRule.WEEKLY,
  count: 23,
})
rule.toText()
;('every week for 23 times')

Provides a hint on whether all the options the rule has are convertible to text.

Constructs an RRule instance from text.

rule = RRule.fromText('every day for 3 times')

Parse text into options:

options = RRule.parseText('every day for 3 times')
// {freq: 3, count: "3"}
options.dtstart = datetime(2000, 2, 1)
var rule = new RRule(options)

new RRuleSet([(noCache = false)])

The RRuleSet instance allows more complex recurrence setups, mixing multiple rules, dates, exclusion rules, and exclusion dates.

Default noCache argument is false, caching of results will be enabled, improving performance of multiple queries considerably.

Include the given rrule instance in the recurrence set generation.

Include the given datetime instance dt in the recurrence set generation.

Include the given rrule instance in the recurrence set exclusion list. Dates which are part of the given recurrence rules will not be generated, even if some inclusive rrule or rdate matches them. NOTE: EXRULE has been (deprecated in RFC 5545)[https://icalendar.org/iCalendar-RFC-5545/a-3-deprecated-features.html] and does not support a DTSTART property.

Include the given datetime instance dt in the recurrence set exclusion list. Dates included that way will not be generated, even if some inclusive rrule or rdate matches them.

Sets or overrides the timezone identifier. Useful if there are no rrules in this RRuleSet and thus no DTSTART.

Same as RRule.prototype.all.

Same as RRule.prototype.between.

Same as RRule.prototype.before.

Same as RRule.prototype.after.

Get list of included rrules in this recurrence set.

Get list of excluded rrules in this recurrence set.

Get list of included datetimes in this recurrence set.

Get list of excluded datetimes in this recurrence set.

rrulestr(rruleStr[, options])

The rrulestr function is a parser for RFC-like syntaxes. The string passed as parameter may be a multiple line string, a single line string, or just the RRULE property value.

Additionally, it accepts the following keyword arguments:

cache

If true, the rruleset or rrule created instance will cache its results. Default is not to cache.

dtstart

If given, it must be a datetime instance that will be used when no DTSTART property is found in the parsed string. If it is not given, and the property is not found, datetime.now() will be used instead.

unfold

If set to true, lines will be unfolded following the RFC specification. It defaults to false, meaning that spaces before every line will be stripped.

forceset

If set to true, an rruleset instance will be returned, even if only a single rule is found. The default is to return an rrule if possible, and an rruleset if necessary.

compatible

If set to true, the parser will operate in RFC-compatible mode. Right now it means that unfold will be turned on, and if a DTSTART is found, it will be considered the first recurrence instance, as documented in the RFC.

tzid

If given, it must be a string that will be used when no TZID property is found in the parsed string. If it is not given, and the property is not found, 'UTC' will be used by default.

• RRule has no byday keyword. The equivalent keyword has been replaced by the byweekday keyword, to remove the ambiguity present in the original keyword.
• Unlike documented in the RFC, the starting datetime, dtstart, is not the first recurrence instance, unless it does fit in the specified rules. This is in part due to this project being a port of python-dateutil, which has the same non-compliant functionality. Note that you can get the original behavior by using a RRuleSet and adding the dtstart as an rdate.

var rruleSet = new RRuleSet()
var start = datetime(2012, 2, 1, 10, 30)

// Add a rrule to rruleSet
rruleSet.rrule(
  new RRule({
    freq: RRule.MONTHLY,
    count: 5,
    dtstart: start,
  })
)

// Add a date to rruleSet
rruleSet.rdate(start)

• Unlike documented in the RFC, every keyword is valid on every frequency. (The RFC documents that byweekno is only valid on yearly frequencies, for example.)

rrule.js is implemented in Typescript. It uses JavaScript Standard Style coding style.

To run the code, checkout this repository and run:

$ yarn

To run the tests, run:

$ yarn test

To build files for distribution, run:

$ yarn build

• Jakub Roztocil (@jkbrzt)
• Lars Schöning (@lyschoening)
• David Golightly (@davigoli)

Python dateutil is written by Gustavo Niemeyer.

See LICENCE for more details.

• https://rrules.com — RESTful API to get back occurrences of RRULEs that conform to RFC 5545.