Article 51 Time
Except in the case of the time limit imposed under rule 42(1), the time for doing any act may (whether it has already expired or not) be extended–
with the leave of the Tribunal or the Chairman, or
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.
A party in whose favour time is extended by consent under paragraph (1)(b) above shall, as soon as may be practicable after the necessary consents have been obtained, serve notice thereof on the Secretary.
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.