class Chronic::RepeaterWeekday

def offset(span, amount, pointer)
  direction = pointer == :future ? 1 : -1
  num_weekdays_passed = 0; offset = 0
  until num_weekdays_passed == amount
    offset += direction * DAY_SECONDS
    num_weekdays_passed += 1 if is_weekday?((span.begin+offset).wday)
  end
  span + offset
end