class Chronic::RepeaterMonth

def offset_by(time, amount, pointer)
  direction = pointer == :future ? 1 : -1
  amount_years = direction * amount / YEAR_MONTHS
  amount_months = direction * amount % YEAR_MONTHS
  new_year = time.year + amount_years
  new_month = time.month + amount_months
  if new_month > YEAR_MONTHS
    new_year += 1
    new_month -= YEAR_MONTHS
  end
  days = month_days(new_year, new_month)
  new_day = time.day > days ? days : time.day
  Chronic.construct(new_year, new_month, new_day, time.hour, time.min, time.sec)
end