(1) The time for doing any act may whether it has already expired or not, be extended¡V
(a) with the leave of the tribunal or the chairman; or
(b) by the consent in writing of all parties, except where the tribunal or chairman has fixed the time by order or (if the time is prescribed by these rules) has directed that it may not be extended or further extended without leave:
Provided that the time limited under rule 19(1) shall not be extended without leave.
(2) A party in whose favour time is extended by consent under paragraph (1) shall, as soon as practicable after the necessary consents have been obtained, give the clerk written notice thereof.
(3) Where the last day for the doing of any act falls on a day on which the office is closed and by reason thereof the act cannot be done on that day, it may be done on the next day on which the office is open.