In computing any period of time prescribed or allowed by the rules in this Chapter, Service Oklahoma does not count the date of the act, or event, from which the period of time begins to run. But Service Oklahoma does include the last day of the period unless it is a Saturday, Sunday, legal holiday as defined by the Oklahoma Statutes, or any other day Service Oklahoma does not remain open until 4:00 p.m. In this case, the period shall run through the end of the next day that Service Oklahoma is open until 4:00 p.m. The Director may extend any time period established by the rules in this Title.
Okla. Admin. Code § 260:135-1-10