It's best to start planning and buying for Thanksgiving dinner at least a week in advance. This will give you enough time to purchase all the necessary ingredients and make any necessary preparations. You can also start preparing dishes that can be made ahead of time, such as cranberry sauce or pie crusts, to save time on the day of the meal. If you decide to go with a meal delivery service, you should order this as soon as possible – ideally at the start of November.