(a) Unless specifically stated otherwise, the term days, as used in this Part, shall mean calendar days.

(b) The date upon which personal service of the request for review was made upon the respondent shall be excluded in the computation of the period in which service of the answer or answer and cross-appeal must be made. If the answer or answer and cross-appeal has been served by mail upon petitioner or petitioner's counsel, three days shall be added to the period in which an answer to the cross-appeal or a reply may be served and filed pursuant to this Part. If the last day for service of any paper permitted under this Part falls on a Saturday or Sunday, service may be made on the following Monday; and if the last day for such service falls on a legal holiday, service may be made on the following business day.