While frozen, a turkey is safe indefinitely. As soon as it begins to thaw, bacteria that may have been present before freezing will begin to grow again. There are three safe ways to defrost a turkey: in the refrigerator, in cold water, and in a microwave oven.
Refrigerator Thawing (Recommended)
The USDA recommends thawing your turkey in the refrigerator. This is the safest method because the turkey will thaw at a consistent, safe temperature. This method takes some time, so allow one day for each 4 - 5 pounds of weight. If your turkey weighs 16 pounds, it will take about four days to thaw. Once thawed, the turkey is safe for another two days, so you can start thawing it six days before thanksgiving (the Friday before Thanksgiving).