Get person's age in Ruby

Question

I\'d like to get a person\'s age from its birthday. now - birthday / 365 doesn\'t work, because some years have 366 days. I came up with the following code:

Answer 1

Here's my solution which also allows calculating the age at a specific date:

def age on = Date.today
  (_ = on.year - birthday.year) - (on < birthday.since(_.years) ? 1 : 0)
end

Answer 2

  def birthday(user)
    today = Date.today
    new = user.birthday.to_date.change(:year => today.year)
    user = user.birthday
    if Date.civil_to_jd(today.year, today.month, today.day) >= Date.civil_to_jd(new.year, new.month, new.day)
      age = today.year - user.year
    else
      age = (today.year - user.year) -1
    end
    age
  end

Answer 3

If you don't care about a day or two, this would be shorter and pretty self-explanitory.

(Time.now - Time.gm(1986, 1, 27).to_i).year - 1970

Answer 4

One liner in Ruby on Rails (ActiveSupport). Handles leap years, leap seconds and all.

def age(birthday)
  (Time.now.to_s(:number).to_i - birthday.to_time.to_s(:number).to_i)/10e9.to_i
end

Logic from here - Calculate age in C#

_{Assuming both dates are in same timezone, if not call utc() before to_s() on both.}

Answer 5

The following seems to work (but I'd appreciate it if it was checked).

age = now.year - bday.year
age -= 1 if now.to_a[7] < bday.to_a[7]

Answer 6

Because Ruby on Rails is tagged, the dotiw gem overrides the Rails built-in distance_of_times_in_words and provides distance_of_times_in_words_hash which can be used to determine the age. Leap years are handled fine for the years portion although be aware that Feb 29 does have an effect on the days portion that warrants understanding if that level of detail is needed. Also, if you don't like how dotiw changes the format of distance_of_time_in_words, use the :vague option to revert to the original format.

Add dotiw to the Gemfile:

gem 'dotiw'

On the command line:

bundle

Include the DateHelper in the appropriate model to gain access to distance_of_time_in_words and distance_of_time_in_words_hash. In this example the model is 'User' and the birthday field is 'birthday.

class User < ActiveRecord::Base
  include ActionView::Helpers::DateHelper

Add this method to that same model.

def age
  return nil if self.birthday.nil?
  date_today = Date.today
  age = distance_of_time_in_words_hash(date_today, self.birthday).fetch("years", 0)
  age *= -1 if self.birthday > date_today
  return age
end

Usage:

u = User.new("birthday(1i)" => "2011", "birthday(2i)" => "10", "birthday(3i)" => "23")
u.age