TRCP4: Holiday and Weekend Deadline Extensions - When does this apply, when not?

Tex. R. Civ. P. 4 (four)

TEXT OF RULE 4. COMPUTATION OF TIME

In computing any period of time prescribed or allowed by these rules, by order of court, 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 to be included.

The last day of the period so computed is to be included, unless it is 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.

Saturdays, Sundays and legal holidays shall not be counted for any purpose in any time period of five days or less in these rules, except that Saturdays, Sundays and legal holidays shall be counted for purpose of the three-day periods in Rules 21 and 21a, extending other periods by three days when service is made by registered or certified mail or by telephonic document transfer, and for purposes of the five-day periods provided for under Rules 748, 749, 749a, 749b, and 749c.

Note that this rule refers to service by telephonic document transfer, but does not mention the word fax, facsimile transmission, or email.