person.rb

require 'date'
require 'active_support/all'

class Person
  attr_accessor :name, :birthdate, :favorite_color

  def initialize(name, birthdate, favorite_color)
    @name = name
    @birthdate = birthdate
    @favorite_color = favorite_color
  end

  def introduce_yourself!
    "Hallo, mein name ist #{@name}, meine lieblingsfarbe ist: #{@favorite_color}!"
  end

  def age
    today = Date.today
    birthdate = Date.parse(@birthdate)
    years = (today.year - birthdate.year)
    birthday_this_year = birthdate + years.years
    if birthday_this_year >= today
      years - 1
    else
      years
    end
  end
end

person1 = Person.new("Marion", "11.02.1980", "green")
person2 = Person.new("Katrin", "11.02.1970", "green")

puts person1.age
puts person2.introduce_yourself!