Tex. Government Code § 311.014: COMPUTATION OF TIME.

(a) In computing a period of days, the first day is excluded and the last day is included.

(b) If the last day of any period is a Saturday, Sunday, or legal holiday, the period is extended to include the next day that is not a Saturday, Sunday, or legal holiday.

(c) If a number of months is to be computed by counting the months from a particular day, the period ends on the same numerical day in the concluding month as the day of the month from which the computation is begun, unless there are not that many days in the concluding month, in which case the period ends on the last day of that month.

Acts 1985, 69th Leg., ch. 479, Sec. 1, eff. Sept. 1, 1985.