(a) This section states how to compute a period of time prescribed or allowed by this Part, by any order of the agency, 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. The last day of the period is included. However, if the last day of the time period would not be a business day as defined by Section 552.0031 of the Texas Government Code, the period is extended until the next day that is a business day.(b) A time period described by statute or this Part to be a certain number of business days is calculated under subsection (a) of this section without including any day within that time period that is not a business day as defined by Section 552.0031 of the Texas Government Code.(c) A document required to be filed or served by a deadline established by statute or this part is filed or served when it is actually received. A document may be deemed to be filed or served when it is deposited with the United States Postal Service, properly addressed to the recipient, with all postage prepaid. The date of the postmark on the envelope for the document is presumed to be the date the document was deposited with the United States Postal Service.(d) A document filed or served by delivery to the United States Postal Service is presumed to have been filed before 5:00 p.m. on the date indicated by the postmark.