13.—(1) The date of giving of any formal communication under these Regulations which is sent by—
(a)a registered post service (as defined in section 125(1) (interpretation)) of the Postal Services Act(1); or
(b)a postal service which provides for the delivery of the document to be recorded,
is the date of sending.
(2) Where these Regulations authorise or require something to be done within a specified period of time and that period expires on a non working day, the period of time is to be treated as expiring on the next working day after that day.