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

The answers so far are kinda weird. Your original attempt was pretty close to the right way to do this:

birthday = DateTime.new(1900, 1, 1)
age = (DateTime.now - birthday) / 365.25 # or (1.year / 1.day)

You will get a fractional result, so feel free to convert the result to an integer with to_i. This is a better solution because it correctly treats the date difference as a time period measured in days (or seconds in the case of the related Time class) since the event. Then a simple division by the number of days in a year gives you the age. When calculating age in years this way, as long as you retain the original DOB value, no allowance needs to be made for leap years.

Answer 2

DateHelper can be used to get years only

puts time_ago_in_words '1999-08-22'

almost 20 years

Answer 3

I know I'm late to the party here, but the accepted answer will break horribly when trying to work out the age of someone born on the 29th February on a leap year. This is because the call to birthday.to_date.change(:year => now.year) creates an invalid date.

I used the following code instead:

require 'date'

def age(dob)
  now = Time.now.utc.to_date
  now.year - dob.year - ((now.month > dob.month || (now.month == dob.month && now.day >= dob.day)) ? 0 : 1)
end

Answer 4

To account for leap years (and assuming activesupport presence):

def age
  return unless birthday
  now = Time.now.utc.to_date
  years = now.year - birthday.year
  years - (birthday.years_since(years) > now ? 1 : 0)
end

years_since will correctly modify the date to take into account non-leap years (when birthday is 02-29).

Answer 5

I like this one:

now = Date.current
age = now.year - dob.year
age -= 1 if now.yday < dob.yday

Answer 6

  def computed_age
    if birth_date.present?
      current_time.year - birth_date.year - (age_by_bday || check_if_newborn ? 0 : 1)
    else
      age.presence || 0
    end
  end


  private

  def current_time
    Time.now.utc.to_date
  end

  def age_by_bday
    current_time.month > birth_date.month
  end

  def check_if_newborn
    (current_time.month == birth_date.month && current_time.day >= birth_date.day)
  end```