When calculating deadlines, TREC and Texas REALTORS® contracts use calendar days, not business days.
Although calculating deadlines for the delivery of the earnest money and the termination option fee use calendar days, the One to Four Family Residential Contract (Resale) (TXR 1601) allows that if the final day for delivery of those funds falls on a weekend or legal holiday, the deadline is moved to the next day that is not a weekend or legal holiday.
The rest of the contract deadlines do not change if the final day falls on a weekend or holiday. Watch the below video for a refresher on how to count those days.
The best way I have learned (and use) to count the days is to know that the Effective Date is Day ZERO… then counting is easy.