PDFWAC 246-10-105
Computation of time.
(1) When computing a period of time prescribed or allowed by an applicable statute or rule, the day of the act, event, or default from which the designated period of time begins to run is not included.
(2) The last day of the computed period is included unless the last day is a Saturday, Sunday, or legal holiday.
(3) When the last day is a Saturday, Sunday, or legal holiday, the period ends at 5:00 p.m. on the next day which is not a Saturday, Sunday, or legal holiday.
(4) When the period of time prescribed or allowed is seven days or less, any intermediate Saturday, Sunday, and legal holiday is excluded from the computation.