Unless otherwise required by law, in computing any period of time set forth in this chapter, the date of the act, event, or default after which the designated period of time begins to run is not to be included. The last day of the period so computed is to be included, unless it is a Saturday, Sunday, or a state legal holiday, in which event the period runs until the end of the next day which is not a Saturday, Sunday, or a state legal holiday. Time limits shall be computed using calendar days rather than business days.
7 Tex. Admin. Code § 93.202