Ruby Date Recurrence Library - Allows easy creation of recurrence rules and fast querying
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ice_cube - Easy schedule expansion

Build Status Gem Version

gem install ice_cube

ice_cube 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 ice_cube quickly figure out whether the schedule falls on a certain date (.occurs_on?), or what times it occurs at (.occurrences, .first, .all_occurrences).

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

schedule = = do |s|
  s.add_exception_time(now +

# 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]

# 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 + 3.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 +, now + 2.days]
schedule.last    # now + 2.days

# or the next occurrence
schedule.next_occurrence(from_time)     # defaults to
schedule.next_occurrences(3, from_time) # defaults to
schedule.remaining_occurrences          # for terminating schedules

# or the previous occurrence
schedule.previous_occurrences(3, from_time)

# or include prior occurrences with a duration overlapping from_time
schedule.next_occurrences(3, 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 count or until on the recurrence rules. Setting end_time on the schedule just sets the duration (from the start time) for each occurrence.

Time Zones and ActiveSupport vs. Standard Ruby Time Classes

ice_cube works great without ActiveSupport but only supports the environment's single "local" time zone (ENV['TZ']) or UTC. To correctly support multiple time zones (especially for DST), you should require 'active_support/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,, time.in_time_zone(tz))
  • DateTime (deprecated) and Date are converted to a Time.local


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

It also supports partial serialization to/from ICAL. RDATE are not supported yet.

yaml = schedule.to_yaml

hash = schedule.to_hash

ical = schedule.to_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 day_of_month(31)).

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