From: "Berger, Daniel" <djberge@...>
Date: 2003-01-30T03:03:52+09:00
Subject: Re: Date math lib?

> -----Original Message-----
> From: Chris Morris [mailto:chrismo@clabs.org] 
> Sent: Wednesday, January 29, 2003 10:25 AM
> To: ruby-talk@ruby-lang.org
> Subject: Date math lib?
> 
> 
> I'm in need of some date math routines -- primarily a way to 
> add/subtract years from a date, which appears to be more than 
> just a no-brainer routine to do it Right(TM) (or maybe my 
> brain is in over-complication mode). Searching RAA and the 
> archives didn't come up with much.
> 
> Chris
> http://clabs.org
> 
>

Generally speaking, Time, Date and ParseDate can accomplish all of your
date-time calculation needs.

For your example, here's one solution (there may be a better one):

years_to_subtract = 34
d1 = Date.new(2003,1,29)
d1.year -> 2003
d2 = d1 << (years_to_subtract * 12)
d2.year -> 1969

The << method subtracts months (hence the *12).  I don't know of a way to
subtract years.

On another note, I noticed something wonky with ParseDate in Windows
(1.6.7):

require "parsedate"
x = Time.now
a = ParseDate.parsedate("#{x}").slice(0..5)

In *nix, a[0] is 2003
In Windows, however, I get nil.

Any ideas anyone?

Regards,

Dan