When Rev. Fordwick and Rev. Prissom arrive, John greets them with "good morning," despite having established in the previous scene that it was mid-afternoon.
At 35:13, although Grandpa is supposed to be driving the truck, it is clearly a stand-in for Will Geer.
At 2:19, when Rev. Fordwick is talking to Reverend Prissom in the car, a crew member's hand can be seen grabbing the seat behind Reverend Prissom. In an earlier shot of the car, it's obvious that nobody is in the back seat.
When John comes home, many comments make it seem like the family has been waiting a long time and John Boy says they've been waiting for the reverend since lunchtime, making it seem like it's late afternoon. When the minister and his escort arrive, John says the visitors were expected 2-3 hours before and when the minister hears they are planning to go swimming, he questions them going swimming on the Sabbath afternoon. However, when the visitors arrived, John greeted them by saying 'morning,' contrary to all other indications that it was afternoon.