[Newbies] a Timetable

[paolo.bernardi.67 at gmail.com]

I'm trying to realize a system that helps
on booking the reservations requests
of tennis plygrounds in a tennis club.

Every club has its not-so-simple opening timetable.
I want to let user building timetables of any complexity degree,
say: with a lot of rules.

So I start handling blocks like:
[ :time | time asTime >= '8:30 am' asTime]
thinking that they will be called many many times,
and many many times will be performed the same parsing of the same 
string '8:30'.

The way I'm following is using TimeRule objects
instead of "raw" BlockCLosures.

TimeRule evaluates the "asTime" value and caches it for late re-use.
At the end the "optimization" meant creating specialized objects.

Does anyone know about a library that implements time ranges?
Not as Duration's, that occurs at a given time,
but ranges that apply to any time
(i.e. from January to June from 8:30 am to 5 pm
but from June to December from 9 am to 10 pm).