Get person's age in ruby

Question

I'd to get a person's age from it's birthday. now - birthday / 365 doesnt work, because some year has 366 days. I came up with following code:

now = Date.today
year = now.year - birth_date.year

if (date+year.year) > now
  year = year - 1
end

Is there a more rubyish way to calculate age?

Answer 1

Use this:

def age
  now = Time.now.utc.to_date
  now.year - birthday.year - (birthday.to_date.change(:year => now.year) > now ? 1 : 0)
end

Answer 2

I've found this solution to work well and be readable for other people:

    age = Date.today.year - birthday.year
    age -= 1 if Date.today < birthday + age.years #for days before birthday

Easy and you don't need to worry about handling leap year and such.

Answer 3

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 4

I'm a ruby newbie. I tried to answer the question before checking out the other replies. It seems to work but I'd appreciate it if anyone check or point out what could be problematic with my answer..

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

Answer 5

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 (in a Rails project) instead:

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 6

  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