(1) The time within which any act shall be done, as provided by these rules, is computed by excluding the first day and including the last, unless the last day is a Saturday, Sunday or a legal holiday, or a day when the board is closed for business under WAC 461-08-320(3), and then it is excluded and the next succeeding day which is neither a Saturday, Sunday nor a legal holiday, or a day when the board is closed for business under WAC 461-08-320(3) is included. When the period of time prescribed or allowed is less than seven days, intermediate Saturdays, Sundays and legal holidays are excluded in the computation.

(2) This section also pertains to the period for filing with the board any petition for review, petition for rule making, petition for declaratory ruling or any other adjudication authorized by this chapter.