In computing any period of time prescribed or allowed by Tex. Admin. Code, Title 22, Part 10, by Order of the Commission, or by any applicable statute, the period shall begin on the day after the act, event, or default in controversy and conclude on the last day the act occurred, unless it be a Saturday, Sunday, or legal holiday, in which event the period runs until the end of the next day which is not a Saturday, Sunday, or legal holiday.
22 Tex. Admin. Code § 201.8