class ActiveSupport::TimeZone

def parts_to_time(parts, now)
  raise ArgumentError, "invalid date" if parts.nil?
  return if parts.empty?
  if parts[:seconds]
    time = Time.at(parts[:seconds])
  else
    time = Time.new(
      parts.fetch(:year, now.year),
      parts.fetch(:mon, now.month),
      parts.fetch(:mday, parts[:year] || parts[:mon] ? 1 : now.day),
      parts.fetch(:hour, 0),
      parts.fetch(:min, 0),
      parts.fetch(:sec, 0) + parts.fetch(:sec_fraction, 0),
      parts.fetch(:offset, 0)
    )
  end
  if parts[:offset] || parts[:seconds]
    TimeWithZone.new(time.utc, self)
  else
    TimeWithZone.new(nil, self, time)
  end
end