class Date

@return [Integer] the age in days for a given date.

@example

date=Date.new(1980,10,31)
date.age_in_days => 11124

@example of custom dates

date=Date.new(1980,10,31)

valentines = Date.new(2011,02,14)
date.age_in_days(valentines) => 11063

halloween = Date.new(2011,10,31)
date.age_in_days(halloween) => 11322

new_years_eve = Date.new(2011,12,31)
date.age_in_days(new_years_eve) => 11383

# File lib/sixarm_ruby_date_age.rb, line 29
def age_in_days(compare_date = Date.today)
  (compare_date.is_a? Date) or raise ArgumentError, "compare_date must be a date"
  (compare_date - self).to_i
end

@return [Integer] the age in years for a given date.

@example

y = Date.today.year
m = Date.today.month
d = Date.today.mday
date = Date.new(y - 30, m, day)
date.age_in_years => 30

@example of custom dates

date=Date.new(1980,10,31)

valentines = Date.new(2011,02,14)
date.age_in_years_on(valentines) => 30  # before the birthday

halloween = Date.new(2011,10,31)
date.age_in_years_on(halloween) => 31  # on the birthday is one year older

new_years_eve = Date.new(2011,12,31)
date.age_years(new_years_eve) => 31  # after the birthday is one year older

# File lib/sixarm_ruby_date_age.rb, line 60
def age_in_years(compare_date = Date.today)
  (compare_date.is_a? Date) or raise ArgumentError, "compare_date must be a date"
  return 0 if self == compare_date
  age = compare_date.year - self.year
  min, max = [self, compare_date].sort
  age -= 1 if max.month < min.month or (max.month == min.month and max.day < min.day)
  age
end