If you are planning to purchase a new dining room set for Thanksgiving, you are up against it now. You need to have made a decision by this time. If you have not, then you should be very careful not to rush into something with which you will be unhappy later.
For most furniture retailers, 6-8 weeks is the time frame for getting merchandise in for delivery. You may luck out, though, if you find a formal dining set you like that also happens to be in your furniture retailer's warehouse and ready for shipping.
A couple of quick reminders if you are a last minute dining buyer:
Measure measure measure!! Getting the formal dining set delivered only to find out you can't pull out the chairs or fit the china cabinet can be frustrating.
Get what you like. Don't settle for a set just because it is in stock. In the long run you will regret it.
Put the leaf in and take it out a couple of times before the big Turkey Day dinner. Make sure everything works so that if your table needs servicing you can get it handled before the big day.
Hope this helps,
The Furniture Guy