From: "David A. Black" <dblack@...>
Date: 2005-08-30T02:21:44+09:00
Subject: Re: Date problem.

Hi --

On Tue, 30 Aug 2005, Joe Cheng wrote:

> ober wrote:
>
>> I have read over the man pages and can not seem to find a way to do the 
>> following
>> 
>> -----php---------------
>> $lastmonth = mktime(0, 0, 0, date("m")-1, date(01),  date("Y"));
>> $name = date('Y-m-d', $lastmonth);
>> echo "$name\n";
>> ----php----------------
>> 
>> Where the first day of the previous month is listed.
>> In this case you would get 2005-07-01
>
> A literal translation to Ruby:
> lastmonth = Date.new(Date.today.year, Date.today.month - 1)
> name = lastmonth.to_s
> puts name
>
> However, this will give you the wrong answer in January.  Here's one that 
> accounts for January:
>
> year, lastmonth = Date.today.year, Date.today.month - 1
> year, lastmonth = year - 1, 12 if lastmonth == 0
> puts Date.new(year, lastmonth).to_s

I think my answer probably suffered from the January bug.  Here's
another way, addressing that problem in a slightly different way from
yours (less work :-)

   irb(main):035:0> d = Date.today << 1
   => #<Date: 4907161/2,0,2299161>
   irb(main):036:0> Date.new(d.year, d.month, 1).to_s
   => "2005-07-01"

January test:

   irb(main):037:0> d = Date.new(2005,1,15) << 1
   => #<Date: 4906709/2,0,2299161>
   irb(main):038:0> Date.new(d.year, d.month, 1).to_s
   => "2004-12-01"


David

-- 
David A. Black
dblack@wobblini.net