The ideal temperature for a freezer is 0 degrees Fahrenheit. Temperatures between 0 and 32 degrees Fahrenheit can prevent spoilage, but flavor, texture and color degrade within this range.
If the freezer power goes off, foods can stay frozen between one to four days. To hold in the cold, keep the freezer closed, fully stocked and covered in insulating blankets. Fluctuating temperatures let food spoil and increase the risk of illness.
The modern freezer replaced the icebox, which featured a cabinet made from insulating materials, a drawer for a large chunk of ice and a compartment for groceries. Iceboxes fell out of style during the 1930s.