From: Brian Adkins <lojicdotcomNOSPAM@...>
Date: 2007-03-15T01:45:06+09:00
Subject: Re: Calculating the age given DOB

Reid Thompson wrote:
> On Wed, 2007-03-14 at 23:55 +0900, Deniz Dogan wrote:
>> Hello, fellow rubyists.
>>
>> I have a problem. I'm trying to write a simple program which calculates 
>> the age of a person given the person's date of birth in an instance of a 
>> Date class. I have no idea what is the best way to do this. I don't feel 
>> like using any ugly "hacks" to do it, and I wonder if there is any good 
>> (perhaps mathematical) algorithm out there to solve the problem.
>>
>> --Deniz Dogan
>>
> rthompso@jhereg:~$ irb
> irb(main):001:0> require 'date'
> => true
> irb(main):002:0>  bd = Date.new(1966, 1, 21)
> => #<Date: 4878293/2,0,2299161>
> irb(main):003:0>  today = Date.new(2007,3,14)
> => #<Date: 4908347/2,0,2299161>
> irb(main):004:0>  age = today.year - bd.year
> => 41
> 
> 

Consider when today.month < bd.month - you'll have an off-by-one error.