(a) Except as otherwise provided by law, the time by which any person is required or allowed to act under any statute, rule, or order may be extended by the decisional authority for good cause, upon a motion made before the expiration of the period prescribed or previously extended.

(b) If any motion for extension of time is made after the expiration of a specified time period, the decisional authority may permit performance of the act required or allowed, if the movant shows extraordinary circumstances sufficient to justify the failure to act in a timely manner.