From: Kaldrenon <kaldrenon@...>
Date: 2008-07-19T01:20:12+09:00
Subject: Finding the date of an event based on related events.

Hi all,

I'm doing some planning to write a simple utility program for
maintaining my schedule. The basic scenario is that, in my job, I have
a series of multi-stage procedures to perform, and for each instance
of the procedure, the stages need to happen a fixed number of business
days apart (i.e, if step one happens on Monday, step two is Friday,
but if step one is Tuesday, step two will be the following Monday). As
one of the first steps of the program, I'm going to write a script to
quickly spit out the calendar dates of all steps given the date of the
first and the relative date (in business days) of all the others.

My question is, can you help me drum up a 'smart' way to take weekends
and holidays into account? I know that with Ruby's Date class you can
use the - (minus) operator to subtract x days from the date of an
existing event. which is how I can find the exact date once I've
determined the number of total days it will be before it has been x
business days.

But the "human" solution to the problem isn't very efficient -
iterating over the days with a counter, checking Date.wday, ignoring
days that return 0 and 6, and spitting back the date at which the
counter reaches x. I'd like to find a more elegant and computationally
efficient solution.

If you've worked out this problem before, or a better solution seems
readily available to you, I'd love input. If my explanation was
unclear, I'll gladly clarify anything.

-Andrew Fallows