A simple age calculator for Ruby. Comes with age validator for ActiveModel.

You might think calculating age from a birthday is easy, but you'd be wrong - there is so much confusion on the topic, and sadly, many people are doing it wrong. Even right ways can look really complicated.

Here's the simplest, cleanest way:

(today.to_s(:number).to_i - birthday.to_s(:number).to_i) / 10000

Suppose today is May 16, 2018 and calculate the age of people whose birthdays are May 15, 2000 (should be 18 years old) and May 17, 2000 (should be 17 years old) respectively.

> 20180516 - 20000517
 => 179999
> 179999 / 10000
 => 17
> 20180516 - 20000515
 => 180001
> 180001 / 10000
 => 18

Couldn't be simpler. Note that Ruby truncates the decimal fraction.

AgeCalculator is a small library to do just that.

Add this line to your application's Gemfile:

gem 'age_calculator'

Or install it yourself as:

$ gem install age_calculator

For a basic usage:

birthday = Date.new(2000,1,1)

ac = AgeCalculator.new(birthday)

ac.age
=> 18

ac.age(asof: Date.new(2020,1,1))
=> 20

For a model with a validation on the age:

class Adult < ActiveRecord::Base
  validates :birthday, age: { over: 18 }
end

class Adult < ActiveRecord::Base
  validates :birthday, age: { over: 18, asof: Date.today.beginning_of_year }
end

1. Fork it ( https://github.com/[my-github-username]/age_calculator/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request