Misc. date functions in ruby

misc_date_functions.rb

# Calculate the number of months between two dates
def months_between (start_date=Time.now, end_date=Time.now)
  (end_date.month - start_date.month) + 12 * (end_date.year - start_date.year)
end

# Calculate a person's age
def age_at(date, dob)
  day_diff = date.day - dob.day
  month_diff = date.month - dob.month - (day_diff < 0 ? 1 : 0)
  date.year - dob.year - (month_diff < 0 ? 1 : 0)
end