(a) In computing any period of time prescribed or allowed by the rules in this subchapter, by order of an IHO, or by any applicable statute, the day of the act, event, or default after which the designated period of time begins to run is not included.
(b) Unless otherwise provided by the rules in this subchapter, the last day of the period so computed is included, unless it is a Saturday, Sunday, or legal holiday, in which event the period runs until the end of the next day that is not a Saturday, Sunday, or legal holiday. Saturdays, Sundays, and legal holidays shall not be counted for any purpose in any time period of five days or fewer.
(c) In computing the time periods required for filing a motion for reconsideration, as set forth at §850.87 of this subchapter (relating to Motion for Reconsideration), and for appealing a final decision of an IHO to a court, as set forth at §850.88 of this subchapter (relating to Civil Action), Saturdays, Sundays, and legal holidays are included.

Source Note: The provisions of this §850.89 adopted to be effective May 13, 2019, 44 TexReg 2364