The time within which an appeal, a petition for hearing, a petition for review, or advisement order is to be perfected, under the provisions of the Employment Security Act (Title 50 RCW, as amended) shall be computed by excluding the day of delivery or mailing of the determination, redetermination, denial, order and notice of assessment, or decision and including the last day. If the last day is a Saturday or Sunday or a holiday, as defined in RCW 1.16.050, the appeal, petition for hearing, petition for review or advisement order must be perfected no later than the next business day.