Birthdays date calculator to show num days alive, leap years lived through, average age of a group of people (e.g. your fam). I dunno, fun to write at least.

bdays.rb

require 'date'

today = Date.today

peeps = [
  [:bj, 1983, 1, 18],
  [:angelee, 1983, 12, 27], 
  [:bella, 2004, 11, 17],
  [:anders, 2008, 6, 30],
  [:india, 2012, 2, 23]
]

t = 0
peeps.each do |args|
  name = args.shift
  bday = Date.new(*args)
  leap_years = bday.year.upto(today.year).inject([]) do |sum, y|
    if (y.modulo(4) == 0 && y.modulo(100) != 0) || (y.modulo(4) == 0 && y.modulo(100) == 0 && y.modulo(1000) == 0)
      sum << y
    else
      sum
    end
  end
  num_days = (today - bday).to_i
  years = (num_days.to_f / 365.0).to_i
  remainder_days = num_days - (years * 365) - leap_years.size
  puts '%s is %d days old (%d years, %d days) (leap years lived %s)' % [name, num_days, years, remainder_days, leap_years.join(',')]
  t += num_days
end

total_yrs = t.to_f / 365.0
average_age = total_yrs / peeps.size.to_f

puts
puts 'Collectively, we are:'
puts "\t%d days old" % t
puts "\t%0.2f years old" % total_yrs
puts "\tAverage age %0.2f years old" % average_age

output.txt

bj is 10713 days old (29 years, 120 days) (leap years lived 1984,1988,1992,1996,2000,2004,2008,2012)
angelee is 10370 days old (28 years, 142 days) (leap years lived 1984,1988,1992,1996,2000,2004,2008,2012)
bella is 2739 days old (7 years, 181 days) (leap years lived 2004,2008,2012)
anders is 1418 days old (3 years, 321 days) (leap years lived 2008,2012)
india is 85 days old (0 years, 84 days) (leap years lived 2012)

Collectively, we are:
	25325 days old
	69.38 years old
	Average age 13.88 years old