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Ruby Date Recurrence Library - Allows easy creation of recurrence rules and fast querying

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ice_cube - Easy schedule expansion

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gem install ice_cube

icecube is a ruby library for easily handling repeated events (schedules). The API is modeled after iCalendar events, in a pleasant Ruby syntax. The power lies in the ability to specify multiple rules, and have icecube quickly figure out whether the schedule falls on a certain date (.occurson?), or what times it occurs at (.occurrences, .first, .alloccurrences).

Imagine you want:

Every friday the 13th that falls in October

You would write:

schedule =

Quick Introductions

With ice_cube, you can specify (in increasing order of precedence):

  • Recurrence Rules - Rules on how to include recurring times in a schedule
  • Recurrence Times - To specifically include in a schedule
  • Exception Times - To specifically exclude from a schedule

Example: Specifying a recurrence with an exception time. Requires "rails/activesupport" (

gem install 'activesupport'
require 'ice_cube'
require 'active_support/time'

schedule = = do |s| s.add_recurrence_rule(IceCube::Rule.daily.count(4)) s.add_exception_time(now + end

list occurrences until end_time (end_time is needed for non-terminating rules)

occurrences = schedule.occurrences(end_time) # [now]

or all of the occurrences (only for terminating schedules)

occurrences = schedule.all_occurrences # [now, now + 2.days, now + 3.days]

or check just a single time

schedule.occurs_at?(now + # false schedule.occurs_at?(now + 2.days) # true

or check just a single day

schedule.occurs_on?( # true

or check whether it occurs between two dates

schedule.occurs_between?(now, now + 30.days) # true schedule.occurs_between?(now + 4.days, now + 30.days) # false

or the first (n) occurrences

schedule.first(2) # [now, now + 2.days] schedule.first # now

or the last (n) occurrences (if the schedule terminates)

schedule.last(2) # [now + 2.days, now + 3.days] schedule.last # now + 3.days

or the next occurrence

schedule.next_occurrence(from_time) # defaults to schedule.next_occurrences(4, from_time) # defaults to schedule.remaining_occurrences # for terminating schedules

or the previous occurrence

schedule.previous_occurrence(from_time) schedule.previous_occurrences(4, from_time)

or include prior occurrences with a duration overlapping from_time

schedule.next_occurrences(4, from_time, :spans => true) schedule.occurrences_between(from_time, to_time, :spans => true)

or give the schedule a duration and ask if occurring_at?

schedule =, :duration => 3600) schedule.add_recurrence_rule IceCube::Rule.daily schedule.occurring_at?(now + 1800) # true schedule.occurring_between?(t1, t2)

using end_time also sets the duration

schedule = =, :end_time => start + 3600) schedule.add_recurrence_rule IceCube::Rule.daily schedule.occurring_at?(start + 3599) # true schedule.occurring_at?(start + 3600) # false

take control and use iteration

schedule = schedule.add_recurrence_rule IceCube::Rule.daily.until( + 30) schedule.each_occurrence { |t| puts t }

The reason that schedules have durations and not individual rules, is to maintain compatibility with the ical RFC:

To limit schedules use

on the recurrence rules. Setting
on the schedule just sets the duration (from the start time) for each occurrence.

Time Zones and ActiveSupport vs. Standard Ruby Time Classes

icecube works great without ActiveSupport but only supports the environment's single "local" time zone (

) or UTC. To correctly support multiple time zones (especially for DST), you should require 'activesupport/time'.

A schedule's occurrences will be returned in the same class and time zone as the schedule's start_time. Schedule start times are supported as:

  • Time.local (default when no time is specified)
  • Time.utc
  • ActiveSupport::TimeWithZone (with
  • DateTime (deprecated) and Date are converted to a Time.local


icecube implements its own hash-based .toyaml, so you can quickly (and safely) serialize schedule objects in and out of your data store

It also supports partial serialization to/from

. Parsing datetimes with time zone information is not currently supported.
yaml = schedule.to_yaml

hash = schedule.to_hash IceCube::Schedule.from_hash(hash)

ical = schedule.to_ical IceCube::Schedule.from_ical(ical)

Using your words

ice_cube can provide ical or string representations of individual rules, or the whole schedule.

rule = IceCube::Rule.daily(2).day_of_week(:tuesday => [1, -1], :wednesday => [2])

rule.to_ical # 'FREQ=DAILY;INTERVAL=2;BYDAY=1TU,-1TU,2WE'

rule.to_s # 'Every 2 days on the last and 1st Tuesdays and the 2nd Wednesday'

Some types of Rules

There are many types of recurrence rules that can be added to a schedule:


# every day
schedule.add_recurrence_rule IceCube::Rule.daily

every third day

schedule.add_recurrence_rule IceCube::Rule.daily(3)


# every week
schedule.add_recurrence_rule IceCube::Rule.weekly

every other week on monday and tuesday

schedule.add_recurrence_rule IceCube::Rule.weekly(2).day(:monday, :tuesday)

for programmatic convenience (same as above)

schedule.add_recurrence_rule IceCube::Rule.weekly(2).day(1, 2)

specifying a weekly interval with a different first weekday (defaults to Sunday)

schedule.add_recurrence_rule IceCube::Rule.weekly(1, :monday)

Monthly (by day of month)

# every month on the first and last days of the month
schedule.add_recurrence_rule IceCube::Rule.monthly.day_of_month(1, -1)

every other month on the 15th of the month

schedule.add_recurrence_rule IceCube::Rule.monthly(2).day_of_month(15)

Monthly rules will skip months that are too short for the specified day of month (e.g. no occurrences in February for


Monthly (by day of Nth week)

# every month on the first and last tuesdays of the month
schedule.add_recurrence_rule IceCube::Rule.monthly.day_of_week(:tuesday => [1, -1])

every other month on the first monday and last tuesday

schedule.add_recurrence_rule IceCube::Rule.monthly(2).day_of_week( :monday => [1], :tuesday => [-1] )

for programmatic convenience (same as above)

schedule.add_recurrence_rule IceCube::Rule.monthly(2).day_of_week(1 => [1], 2 => [-1])

Yearly (by day of year)

# every year on the 100th days from the beginning and end of the year
schedule.add_recurrence_rule IceCube::Rule.yearly.day_of_year(100, -100)

every fourth year on new year's eve

schedule.add_recurrence_rule IceCube::Rule.yearly(4).day_of_year(-1)

Yearly (by month of year)

# every year on the same day as start_time but in january and february
schedule.add_recurrence_rule IceCube::Rule.yearly.month_of_year(:january, :february)

every third year in march

schedule.add_recurrence_rule IceCube::Rule.yearly(3).month_of_year(:march)

for programmatic convenience (same as above)

schedule.add_recurrence_rule IceCube::Rule.yearly(3).month_of_year(3)

Hourly (by hour of day)

# every hour on the same minute and second as start date
schedule.add_recurrence_rule IceCube::Rule.hourly

every other hour, on mondays

schedule.add_recurrence_rule IceCube::Rule.hourly(2).day(:monday)

Minutely (every N minutes)

# every 10 minutes
schedule.add_recurrence_rule IceCube::Rule.minutely(10)

every hour and a half, on the last tuesday of the month

schedule.add_recurrence_rule IceCube::Rule.minutely(90).day_of_week(:tuesday => [-1])

Secondly (every N seconds)

# every second
schedule.add_recurrence_rule IceCube::Rule.secondly

every 15 seconds between 12:00 - 12:59

schedule.add_recurrence_rule IceCube::Rule.secondly(15).hour_of_day(12)


The team over at GetJobber have open-sourced RecurringSelect, which makes working with IceCube easier in a Rails app via some nice helpers.

Check it out at



Use the GitHub issue tracker


  • Contributions are welcome - I use GitHub for issue tracking (accompanying failing tests are awesome) and feature requests
  • Submit via fork and pull request (include tests)
  • If you're working on something major, shoot me a message beforehand

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