My results took eight days. My results came back negative which are supposed to be 99.8% accurate for DS. A positive result for DS is less accurate, something like 98.4%. So if you were to receive a positive, you would probably want to confirm that with an amnio. If you don't already know the gender of your baby, then the MaterniT21 test will give you a gender result that is 99.4% accurate. Obviously, the test also checks for a few other abnormalities.
Fortunately, I have also heard of many chomosomally normal babies that have had calcium heart deposits which resolved on their own. Try not to worry, but I would call your lab/OB today and see if those results are in today. They retrieve them online. I can't imagine the holiday would make that much difference in how long it takes because while people were out for the holiday, the DNA extracted from your blood was still replicating.
Good luck and please check back in!