[Ruby] Schedule/calendar library?

[James Moore]

I'm in need of a library that will let me create schedules that implement
things like:

Tues, Wed, Thur from 8am - 5pm
10pm - 5am
Aug 13 - Aug 19, 2006
Every Third Saturday
Holidays (for arbitrary lists of country-specific holidays)

(And test whether or not a particular date/time falls into the schedule,
etc)

Suggestions?  Pretty straightforward to code, but it also seems like I'd be
reinventing the wheel.  Looked at rubyforge, but didn't see anything
interesting when I went looking for "schedule."

 - James