ice_cube is a recurring date library for Ruby. It allows for quick, programatic expansion of recurring date rules.
A simple library to handle recurring events
A library for specifying, quering, and enumerating recurring events for calendars in Ruby.
ScheduleFu allows scheduling events with dates and times.
Runt is a Ruby implementation of temporal patterns by Martin Fowler. Runt provides an API for working with recurring events using set expressions.
RecurringEvent: A ruby library to aid in describing recurrent or patterned sets of dates.
A date recurrence generator for the ruby Date class
A JRuby implementation of RFC 2445 (ical) recurrence rule
Recurring allows you to define Schedules, which can tell you whether or not a given Time falls in the Schedule, as well as being able to return a list of times which match the Schedule within a given range.